Optical disk, optical disk device, and method of reproducing information on optical disk

ABSTRACT

The present invention is aimed at providing an optical disk, an optical disk device, and an optical disk reproduction method, for allowing for stable and efficient reading of address information. The optical disk includes a plurality of tracks each divided into a plurality of recording sectors. Each of the recording sectors includes a header region. The header region includes address information for identifying the position of the corresponding recording sector and address synchronous information for identifying the recording position of the address information for bit synchronization. The address information has been modulated using a run length limit code of a maximum inversion interval of T max  bits (T max  is a natural number), and the address synchronous information includes two patterns of which inversion interval is (T max +3) bits or more, so that the reproduced signal of the address synchronous information is distinguished from the reproduced signal of other information.

TECHNICAL FIELD

[0001] The present invention relates to an optical disk, an optical diskdevice, and an optical disk reproduction method, forrecording/reproducing digital signals.

BACKGROUND ART

[0002] In recent years, optical disk devices have attracted attention asmeans for recording/reproducing a large capacity of data, and are underactive technical developments for achieving higher recording density.

[0003] Presently prevailing rewritable optical disks includespiral-shaped groove tracks composed of concave and convex portions(each having a width of about 50%) formed on a surface of a disksubstrate at a pitch of 1 to 1.6 μm. On the surface of the substrate, athin film including a recording material (e.g., Ge, Sb, and Te in thecase of a phase-change type optical disk) as a component is formed by amethod such as sputtering. The disk substrate is fabricated in thefollowing manner. First, a stamper is produced from a prototype whereconcave grooves and pits for sector addresses and the like are formed bycutting by light beam irradiation. Using such a stamper, the disksubstrates made of polycarbonate and the like are mass-produced. Therewritable optical disks require sector-unit management for datarecording and reproduction. Accordingly, at the fabrication of thedisks, concave and convex portions (pits) are often formed on arecording surface, simultaneously with the formation of guide groovesfor tracking control, so as to record address information of eachsector.

[0004] Each track of the optical disk with the above structure isirradiated with a light beam having a predetermined recording power, soas to form recording marks on the recording thin film. The portionsirradiated with the light beam (the recording marks) have differentoptical characteristics (reflection characteristics) from the otherportions of the recording thin film. Thus, the recorded information canbe reproduced by irradiating the track with a predetermined reproductionpower and detecting light reflected from the recording film.

[0005] In the following description, the pits of physical concave andconvex portions and the recording marks obtained by a change in theoptical characteristics of the recording thin film are genericallyreferred to as “marks”, unless otherwise specified. The pits areread-only marks once formed, while the recording marks are rewritable.At the reproduction of recorded information, the two types of marks areread as changes in the amplitude of reproduction signals. The concaveand convex portions as used herein refers to the shapes as are viewedfrom a reproduction beginning of the optical disk device. In otherwords, the “pits” refer to the convex portions as are viewed from thereproduction head, and the “grooves” also refer to the convex portions.

[0006] Techniques for achieving an optical disk with a high recordingdensity include increasing the recording density in the track directionand increasing the recording density in the linear velocity-direction.

[0007] Increasing the recording density in the track direction includesreducing the distance between tracks (the track pitch). One techniquefor reducing the track pitch is land/groove recording where signals arerecorded both on convex tracks (groove portions) and concave tracks(land portions). The land/groove recording realizes double recordingdensity, compared with the case of recording signals on either thegroove porions or the land portions, if the other conditions are thesame.

[0008] One technique for increasing the recording density in the linearvelocity direction is referred to as mark length recording where bothends of a mark are made to correspond to “1” of modulation data. FIG. 1illustrates an example of the mark length recording in comparison withinter-mark recording. Referring to FIG. 1, a sequence Y representsdigital data modulated using a run length limit code. The run lengthlimit code as used herein refers to a code sequence where the number ofcontinuous “0”s interposed between every adjacent “1”s (hereinbelow,called the zero run) is limited to a predetermined number. The interval(length) from one “1” to the next “1” in the sequence Y is called aninversion interval. The limits, i.e., the minimum and maximum values ofthe inversion interval of the sequence Y are determined by thelimitation of the zero run. Such values are called the minimum inversioninterval and the maximum inversion interval.

[0009] When the sequence Y is recorded using the inter-mark recording(PPM; pit position modulation), the “1” of the sequence Y corresponds toa recording mark 101, and the zero run corresponds to a space 102. Whenthe sequence Y is recorded using the mark length recording (PWM; pulsewidth modulation), the recording state, i.e., whether the recording mark101 or the space 102, is switched by the appearance of “1” in thesequence Y. When the mark length recording is employed, the inversioninterval corresponds to the length of the recording mark 101 or thespace 102.

[0010] When a run length limit code of which the minimum inversioninterval is 2 or more is used, the mark length recording may have anincreased number of bits per unit length, compared with the inter-markrecording. For example, consider the case where the minimum value of thephysical size of a mark which can be formed on a disk (called a markunit) is the same in both the mark length recording and the inter-markrecording. As is observed from FIG. 1, while the inter-mark recordingutilizes three mark units to record data of the minimum code length(three bits, “100”, in the sequence Y), the mark length recordingutilizes only one mark unit. For example, while the recording density inthe inter-mark recording is approximately 0.8 to 1.0 μm/bit, therecording density in the mark length recording is approximately 0.4μm/bit.

[0011] In general, the tracks on the optical disk are divided intorecording sectors which represent minimum access units. Addressinformation is prerecorded on each recording sector as described above.By reading the address information, the access to the recording sectorsfor data recording/reproduction is possible.

[0012]FIG. 2A illustrates a signal format of each recording sector of arewritable optical disk which is in accordance with ISO (see ISO/IEC10090). A recording sector 103 begins with a header 104 where addressinginformation for reading address information is prerecorded by formingconcave and convex portions on the recording surface. A recording field105 stores user data where digital data is modulated using a (2,7)modulation code for the inter-mark recording. FIG. 3 shows a conversiontable of (2,7) modulation codes. As is observed from FIG. 3, by the(2,7) modulation, i-bit digital data (i=2, 3, 4) is converted into a2xi-bit code sequence. The (2,7) modulation codes are run length limitcodes where the zero run is limited between 2 and 7.

[0013]FIG. 2B shows the construction of the header 104. A sector mark SMis provided so that the optical disk device can identify the beginningof the recording sector without clock reproduction by a phase lockedloop (PLL). As shown in FIG. 2C, the sector mark SM includes a patternusing comparatively long marks. Since the sector mark SM has thispredetermined pattern, and the amplitude of the reproduction signalsthereof is large, the sector mark SM is distinguishable from other datarecorded using the inter-mark recording. The position of the header 104is detected by detecting the sector mark SM, thereby to reproduce theaddress information.

[0014] VFO regions VF01 and-VF02 shown in FIG. 2B are provided so thatthe optical disk device can obtain bit synchronization of reproductionsignals using a clock reproduction by the PLL. A 2-zero run sequentialpattern is recorded using the inter-mark recording.

[0015] Address marks AM are provided so that the optical disk device canidentify the byte synchronization of subsequent address fields ID1, ID2,and ID3. Each of the address marks AM includes a pattern as shown inFIG. 2D recorded using the inter-mark recording technique. The patternof the address mark AM includes a pattern of T_(max)+1=9 bits whereT_(max) is a maximum inversion interval of the (2,7) modulation code(T_(max)=8). This pattern does not appear in data recorded by the (2,7)modulation code.

[0016] Each of the address fields ID1, ID2, and ID3 includes: addressinformation composed of track numbers, sector numbers, and the like; andcyclic redundancy check (CRC) codes for error detection during datareproduction, which are subjected to the (2,7) modulation and recordedusing the inter-mark recording.

[0017] A postamble PA is provided to indicate the end of the (2,7)modulated data in the address field ID3.

[0018]FIG. 4 shows an example of signal amplitudes obtained wheninformation recorded on the header 104 is reproduced by the optical diskdevice. As is observed from FIG. 4, the amplitudes of the reproducedsignals are proportional to the lengths of the corresponding marks. Theamplitude of the reproduced signal of the sector mark SM which has along length is larger than that of the reproduced signal of other data.This allows for the identification of the sector mark SM by detectingthe envelope of the reproduced signal waveform, and thus the detectionof the beginning of each recording sector.

[0019] In the above example, all of the (2,7) modulated data is recordedusing the inter-mark recording. However, in an optical disk having theheader 104, when data is recorded using the mark length recording forimproving the recording density, the marks recorded in the addressfields ID1 to ID3 of the header 104 and the marks recorded in therecording field 105 have a certain length determined by the zero runlimitation of the modulation code. Accordingly, the amplitude of thereproduced signal of data recorded using the mark length recordingbecomes large, compared with that recorded using the inter-markrecording where each mark corresponds to the 1-bit long “1”. In the marklength recording, therefore, the difference in the signal amplitude (orthe difference in the pattern) between the sector mark SM and the otherportions becomes small compared with the case of the inter-markrecording. This makes it difficult to detect the beginning of therecording sector 103 by the envelope.

[0020] Moreover, when the above-described address mark AM is used, anerroneous detection of the address mark AM due to an erroneous bit shiftof “1” may occur. For example, a code sequence obtained by the (2,7)modulation of digital data { . . . 10110011 . . . } is converted into {. . . 0100100000001000 . . . } from a conversion table such as thatshown in FIG. 3. At this time, the pattern of the address mark AM is{0100100000000100} as shown in FIG. 2D. If “1” of the above (2,7)modulated pattern shifts by one bit, the resultant pattern is identicalto the address pattern AM, which will cause erroneous detection.

[0021] In view of the foregoing, the objects of the present inventionare to provide an optical disk, an optical disk device, and an opticaldisk reproduction method, where address information can be read reliablyeven when high recording density is achieved by employing mark lengthrecording and the like.

DISCLOSURE OF INVENTION

[0022] The optical disk of the present invention includes a plurality oftracks each divided into a plurality of recording sectors, each of therecording sectors including a header region, wherein the header regionincludes address information for identifying a position of thecorresponding recording sector and address synchronous information foridentifying a recording position of the address information for bitsynchronization. The address information has been modulated using a runlength limit code of a maximum inversion interval of T_(max) bits(T_(max) is a natural number), and the address synchronous informationincludes two patterns of which inversion interval is (T_(max)+3) bits ormore, so that a reproduced signal of the address synchronous informationis distinguished from a reproduced signal of other information. With theabove construction, the above objects are attained.

[0023] In one embodiment, the address synchronous information includes afirst pattern and a second pattern which are different in either aphysical shape or an optical characteristic of a recording surface ofthe optical disk, and the address synchronous information includes onefirst pattern having a length of (T_(max)+3) bits or more and one secondpattern having a length of (T_(max)+3) bits or more.

[0024] The pattern may be a convex portion (pit) formed physically onthe recording surface of the optical disk, and the second pattern is aconcave portion formed physically on the recording surface of theoptical disk.

[0025] The first pattern may be a recording mark formed by changing areflection characteristic of the recording surface of the optical disk,and the second pattern is a space on the recording surface.

[0026] Preferably, a total bit length of the first pattern included inthe address synchronous information and a total bit length of the secondpattern included in the address synchronous information are equal toeach other.

[0027] Preferably, the header region includes four-time repetition ofthe address information and the address synchronous information.

[0028] The optical disk of this invention includes a plurality of trackseach divided into a plurality of recording sectors, each of therecording sectors including a header region, wherein the header regionincludes address information for identifying a position of thecorresponding recording sector, address synchronous information foridentifying a recording position of the address information for bitsynchronization, and clock synchronous information for reproducing aclock signal, the address information has been modulated using a runlength limit code of a minimum inversion interval of T_(min) bits and amaximum inversion interval of T_(max) bits (T_(max) and T_(min) arenatural numbers satisfying T_(max)>T_(min)), the clock synchronousinformation is a sequential pattern of alternate repetition of d-bitlong mark and space (d is a natural number satisfyingT_(min)≦d≦T_(max)), and the address synchronous information includes twopatterns of which inversion interval is (T_(max)+3) bits or more, sothat a reproduced signal of the address synchronous information isdistinguished from a reproduced signal of other information. With theabove construction, the above objects are attained.

[0029] In one embodiment, each of the address synchronous informationand the clock synchronous information includes a first pattern and asecond pattern which are different in either a physical shape or anoptical characteristic of a recording surface of the optical disk, andthe address synchronous information includes one first pattern having alength of (T_(max)+3) bits or more and one second pattern having alength of (T_(max)+3) bits or more.

[0030] In another embodiment, the minimum inversion interval T_(min) is3, the maximum inversion interval T_(max) is 11, and the value d is 3.

[0031] In still another embodiment, the minimum inversion intervalT_(min) is 3, the maximum inversion interval T_(max) is 11, and thevalue d is 4.

[0032] Preferably, the header region includes four-time repetition ofthe clock synchronous information, the address information, and theaddress synchronous information.

[0033] The optical disk comprising a plurality of tracks each dividedinto a plurality of recording sectors, wherein each recording sectorincludes a header region and a postamble region following an end of theheader region, and the postamble region includes a pattern determinedbased on a modulation result of data of the header region. With aboveconstruction, the above objects are attained.

[0034] In one embodiment, the data on the header region is modulatedusing a modulation code for performing a conversion in a table based ona state, the postamble region includes information for identifying thestate.

[0035] The information for identifying the state may be at least onespecific bit having a predetermined value, and a bit located adjacent tothe specific bit has substantially the same value as the predeterminedvalue of the specific bit.

[0036] The optical disk of this invention includes a plurality of trackseach divided into a plurality of recording sectors, wherein eachrecording sector includes a header region, a data recording region, anda postamble region following an end of the data recording region, andthe postamble region includes a pattern determined based on a modulationresult of data of the data recording region. With this construction, theabove objects are attained.

[0037] In one embodiment, the data on the data recording region ismodulated using a modulation code for performing conversion in a tablebased on a state, the postamble region includes information foridentifying the state.

[0038] The information for identifying the state may be at least onespecific bit having a predetermined value, and a bit located adjacent tothe specific bit has substantially the same value as the predeterminedvalue of the specific bit.

[0039] In one embodiment, the recording sector further includes a guarddata recording region following the postamble region for recording dummydata.

[0040] In another embodiment, the data recording region includes datamodulated using a run length limit code of a minimum inversion intervalof T_(min) bits and a maximum inversion interval of T_(max) bits(T_(max) and T_(min) are natural numbers satisfying T_(max)>T_(min)),and the guard data recording region includes a pattern of alternaterepetition of a k-bit long optical mark and a k-bit long optical space(k is a natural number satisfying T_(min)≦k≦T_(max))

[0041] The optical disk of this invention includes a plurality of trackseach divided into a plurality of recording sectors, wherein eachrecording sector includes a header region, and the header regionincludes an address region having a postamble region at an end of theaddress region, and the postamble region has a pattern which ends withnon-pit data or a space. With this construction, the above objects areattained.

[0042] The header region may include a plurality of the address regions.

[0043] The address regions may be located in the middle of grooveportions and land portions of the tracks.

[0044] The optical disk of this invention includes a plurality of trackseach divided into a plurality of recording sectors, wherein eachrecording sector includes a header region, the header region includes aplurality of address regions, each of the address regions includes a VFOregion at a beginning of the address region, and the VFO region has apattern which starts with non-pit data or a space. With thisconstruction, the above objects are attained.

[0045] In one embodiment, the address region includes an addressinformation region where address information is recorded by a marklength recording for identifying a position of the correspondingrecording sector, and the address information is modulated using a runlength limit code of a minimum inversion interval of T_(min) bits and amaximum inversion interval of T_(max) bits (T_(max) and T_(min) arenatural numbers satisfying T_(max)>T_(min)), and non-pit data or a spacehaving a length in a range of T_(min) bits or more and T_(max) bits orless is provided between the address regions.

[0046] The address regions may be located in the middle of grooveportions and land portions of the tracks.

[0047] The optical disk device of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the devicecomprising: means for reading a reproduced signal from the optical disk;address reproduction means for obtaining the address information fromthe reproduced signal; detection means for detecting the sequentialpattern of the clock synchronous information from the reproduced signalto output a detection signal; and address reproduction permit means forpermitting the address reproduction means to perform a read operation ofthe address information based on the detection signal. With thisconstruction, the above objects are attained.

[0048] In one embodiment, the optical disk device further includes:clock generation means for generating a clock signal from the reproducedsignal; and clock reproduction permit signal for permitting the clockgeneration means to perform an operation of generating the clock signalbased on the detection signal.

[0049] The detection means may includes: binary means for converting thereproduced signal into binary data to output the binary data;sampling-means for sampling the binary data at a predetermined frequencyto output digital data; parallel conversion means for converting thedigital data into parallel data of at least m x n bits (m and n arenatural numbers); and a detection table for detecting a predeterminedsequence composed of n-time repetition of an m-bit pattern from theparallel data.

[0050] The optical disk device of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the devicecomprising: means for reading a reproduced signal from the optical disk;clock generation means for generating a clock signal from the reproducedsignal; detection means for detecting the sequential pattern of theclock synchronous information from the reproduced signal to output adetection signal; and clock reproduction permit means for permitting theclock generation means to perform an operation of generating the clocksignal based on the detection signal.

[0051] In one embodiment, the detection means comprises: binary meansfor converting the reproduced signal into binary data to output thebinary data; sampling means for sampling the binary data at apredetermined frequency to output digital data; parallel conversionmeans for converting the digital data into parallel data of at least m xn bits (m and n are natural numbers); and a detection table fordetecting a predetermined sequence composed of n-time repetition of anm-bit pattern from the parallel data.

[0052] The reproduction method of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reading of theaddress information if the sequential pattern is detected; reading theaddress information from the reproduced signal in response to thepermission; and terminating the step of reading the address informationin a predetermined time period after the permission to return to thestep of detecting the sequential pattern. With this construction, theabove objects are attained.

[0053] In one embodiment, the reproduction method further includes thesteps of: permitting reproduction of a clock signal if the sequentialpattern is detected; and reproducing the clock signal from thereproduced signal in response to the permission.

[0054] The reproduction method of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reproduction of aclock signal if the sequential pattern is detected; and reproducing theclock signal from the reproduced signal in response to the permission.With this construction, the above objects are attained.

[0055] The reproduction method of this invention is for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; determining a reproduction mode whether the reproduction mode isan initial mode during a time period from switching-on of the device ora track jump until the address information is first read from thereproduced signal or a normal mode during a time period from the readingof the address information until a next track jump is generated;detecting the sequential pattern of the clock synchronous informationfrom the reproduced signal; permitting reading of the addressinformation if the sequential pattern is detected in the initial mode asa first permitting step; reading the address information from thereproduced signal in response to the permission; generating a sectorpulse if the address information is correctly read; permitting readingof the address information from the reproduced signal based on thesector pulse in the normal mode as a second permitting step; andterminating the reading of the address information to return to the stepof determining a reproduction mode if the address information fails tobe read within a predetermined time period after either the first orsecond permission step. With this construction, the above objects areattained.

BRIEF DESCRIPTION OF DRAWINGS

[0056]FIG. 1 is a view for explaining the mark length recording and theinter-mark recording.

[0057]FIG. 2A is a view illustrating a signal format of a recordingsector of a conventional optical disk.

[0058]FIG. 2B is a view illustrating a header of the conventionaloptical disk.

[0059]FIG. 2C is a view illustrating a recording pattern of a sectormark of the conventional optical disk.

[0060]FIG. 2D is a view illustrating a recording pattern of an addressmark of the conventional optical disk.

[0061]FIG. 3 illustrates a modulation table of (2,7) modulation codes.

[0062]FIG. 4 is a view illustrating an example of reproduced signalwaveforms at the header of the conventional optical disk.

[0063]FIGS. 5A to 5C are views for explaining a construction of anoptical disk of one example according to the present invention.

[0064]FIG. 6 is a view illustrating an exemplary recording pattern of aVFO region of the optical disk of the example according to the presentinvention.

[0065]FIGS. 7A to 7C are views illustrating exemplary recording patternsof an address mark of the optical disk of the example according to thepresent invention.

[0066]FIGS. 8A to 8D are views illustrating exemplary recording patternsof the address mark of the optical disk of the example according to thepresent invention.

[0067]FIG. 9 is a view illustrating an exemplary recording pattern ofthe address mark of the optical disk of the example according to thepresent invention.

[0068]FIG. 10 is a block diagram of an optical disk device of oneexample according to the present invention.

[0069]FIG. 11 is a block diagram of an exemplary inner construction of areproduction system shown in FIG. 10.

[0070]FIG. 12A is a block diagram of an exemplary inner construction ofa VFO detection circuit of the example according to the presentinvention.

[0071]FIG. 12B is a view illustrating the construction of a VFOdetection table in the example according to the present invention.

[0072]FIG. 13 is a timing chart of exemplary waveforms of varioussignals used in the optical disk device of the example according to thepresent invention.

[0073]FIG. 14 is a timing chart of exemplary waveforms of varioussignals used in the optical disk device of the example according to thepresent invention.

[0074]FIG. 15 is a flowchart of an exemplary process after theturning-on of a system control of the optical disk device of the exampleaccording to the present invention.

[0075]FIG. 16 is a flowchart of an exemplary process of the systemcontrol of the optical disk device of the example according to thepresent invention.

[0076]FIG. 17A is a view illustrating a signal format of a recordingsector of an optical disk of another example according to the presentinvention.

[0077]FIG. 17B is a view illustrating a signal format of a header regionof the optical disk of the example according to the present invention.

[0078]FIG. 18A is a block diagram of a modulation circuit for a statemodulation code in the example according to the present invention.

[0079]FIG. 18B is a view illustrating an exemplary content of aconversion table shown in FIG. 18A.

[0080]FIG. 18C is a block diagram of the construction of a demodulationcircuit for the state modulation code in the example according to thepresent invention.

[0081]FIGS. 19A and 19B are views illustrating exemplary recordingpatterns for a postamble in the example according to the presentinvention.

[0082]FIGS. 20A to 20C are views for explaining the construction of anoptical disk of still another example according to the presentinvention.

[0083]FIGS. 21A and 21B are schematic views illustrating exemplaryarrangements of an address region of a header region of the optical diskof the example according to the present invention.

[0084]FIG. 21C is a view illustrating a coupling portion of addressregions shown in FIGS. 21A and 21B.

[0085]FIG. 22A is a schematic view illustrating the case where thecoupling portion of the address regions of the optical disk includesmarks and the marks are ideally formed.

[0086]FIG. 22B is a schematic view illustrating the marks formed on thecoupling portion of the address regions of the optical disk.

[0087]FIGS. 23A and 23B are views illustrating the operation where anoptical spot performs data reproduction along a land track.

[0088]FIGS. 24A to 24H are views illustrating exemplary patterns of apostamble.

[0089]FIG. 25A is a view illustrating a signal format of a recordingsector of an optical disk of still another example according to thepresent invention.

[0090]FIG. 25B is a view illustrating an exemplary pattern recorded on aguard data recording region in the example according to the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0091] Hereinbelow, the present invention will be described by way ofexample with reference to the relevant drawings.

EXAMPLE 1

[0092]FIG. 5A schematically illustrates an optical disk 1 a of the firstexample according to the present invention. As shown in FIG. 5A, theoptical disk 1 a has tracks 1 b formed in a spiral shape. Each track. 1b is divided into recording sectors 1 c in accordance with apredetermined physical format. As shown in FIG. 5A, the recordingsectors 1 c are sequentially arranged in the circumferential directionto form the track 1 b.

[0093]FIG. 5B illustrates a format of each recording sector 1 c of theoptical disk 1 a of the first example according to the presentinvention. Referring to FIG. 5B, the recording sector 1 c starts with aheader region 2 where addressing information for reading addressinformation is prerecorded. A gap region 3, a data recording region 4,and a buffer region 5 respectively follow the header region 2 in thisorder. The gap region 3 has no data recorded thereon, but is used forpower control of a semiconductor laser used for datarecording/reproduction and the like. The data recording region 4 is usedto record user data. Redundant data such as an error correction code isadded to the user data, to form digital data. The digital data ismodulated using a run length limit code where the zero run is limited tothe range of 2 to 10. The modulated data is recorded on the datarecording region 4 using the mark length recording. Such a run lengthlimit code is called the (2,10) modulation code. The buffer region 5 isprovided to absorb a rotational fluctuation of the optical disk and thelike. In the header region 2, information may be recorded as pits in aconcave and convex shape on the recording surface, or as marks opticallyrecorded in substantially the same manner as that used in the recordingon the data recording region.

[0094] As shown in FIG. 5C, the header region 2 is divided into fouraddress regions 6 a, 6 b, 6 c, and 6 d. Each of the address regionsincludes a VFO region, an address mark AM, and an address informationregion ID. For example, the address region 6 a includes a VFO regionVF01, an address mark AM, and an address information region ID1, whilethe address region 6 b includes a VFO region VF02, an address mark AM,and an address information region ID2.

[0095] In the conventional header 104 shown in FIG. 2B, the sector markSM precedes the pattern composed of the VFO region, the address mark AM,and the address field ID which is repeated three times. In this example,no sector mark is recorded on each header region 2, but the addressregion, similar to the above pattern, which is composed of the VFOregion, the address mark AM, and the address information region ID, isrepeated four times.

[0096] The VFO regions VF01, VF02, VF03, and VF04 are used so that anoptical disk device can obtain clock reproduction from reproducedsignals. As shown in FIG. 6, each VFO region has such a sequentialpattern that includes 4-bit long marks and 4-bit long spaces appearingalternately. Each of the VFO regions may have the same length ordifferent lengths. For example, if the VFO region VF01 is made longerthan the other VFO regions VF02, VF03, and VF04, stable clockreproduction is obtained at the beginning of the header region 2.

[0097] Each address mark AM is provided so that the optical disk devicecan identify the position of the subsequent address information regionID to obtain bit synchronization therewith. FIG. 7A shows an example ofthe address mark AM of this example. As shown in FIG. 7A, marks arerecorded on the optical disk using the mark length recording inaccordance with the signal sequence (bit pattern) of the address markAM. The resultant signal to be read has an amplitude in accordance withthe pattern of marks and spaces (portions other than the marks). In thisexample, the address mark AM has a pattern which includes one 14-bitlong mark and one 14-bit long space. The address information regionsID1, ID2, ID3, and ID4 are representatively denoted as an addressinformation region ID.

[0098] With respect to the address information region ID, digital datacomposed-of data including address information such as the track numberand the sector number and a predetermined error detection code addedthereto are recorded using the mark length recording, after the digitaldata are modulated using a (2,10) modulation code.

[0099] Since the maximum inversion interval of the (2,10) modulationcode is 11, no marks or spaces having a length of 12 bits or more areincluded in the pattern in any of the address information regions ID andthe data recording regions. Even if the 11-bit long mark in the addressinformation region ID or the data recording region is erroneouslyreproduced as a 12-bit long mark due to an edge shift of the mark or thelike, and furthermore the 14-bit long mark in the address mark AM iserroneously reproduced as a 13-bit long mark, the one-bit longdifference still exists therebetween. Accordingly, unless the mark/spacein either one of the regions is subjected to an edge shift by 2 or morebits, a failure to detect the 14-bit long mark in the address mark AM oran erroneous detection of a pattern in the address information region IDor the data recording region as a 14-bit long mark will not occur. Inthis way, the address mark AM can be detected without fail by recordingtwo patterns (one mark and one space) having a length of T_(max)+3 bitsor more where T_(max) is the maximum inversion interval.

[0100] As described above, the address mark AM includes two 14-bit longmark/spaces. This pattern reduces the probability of erroneous detectioncompared with a pattern including only one 14-bit long mark or space.Moreover, the pattern including only one 14-bit long mark or space canbe used as a data synchronization detection pattern for the datarecording region 4. This makes it possible, not only to maintain thereliability of the data synchronization detection, but also tofacilitate prevention of the data synchronization detection pattern frombeing erroneously detected as the address mark AM.

[0101]FIGS. 7B and 7C illustrate other examples of the address mark AM.A pattern including two 14-bit long marks as shown in FIG. 7B and apattern including two 14-bit long spaces as shown in FIG. 7C may be usedas the address mark AM. Using the patterns as shown in FIGS. 7B and 7C,however, the entire recording pattern may be made one-sided in thebalance of marks and spaces. If the entire recording pattern becomesone-sided, the low-frequency component of the pattern increases. Theincrease of the low-frequency components of the pattern varies theamount of the reproduced signal components in the servo frequency band,which affects the servo system. Accordingly, the amount of thelow-frequency component of the pattern should preferably be as small aspossible. Thus, the pattern as shown in FIG. 7A is preferable where theappearance of the marks and the spaces is balanced.

[0102]FIGS. 8A to 8D illustrate yet other examples of the address markAM. The address mark AM shown in FIG. 8A has a pattern composed of{6-bit long mark, 14-bit long space, 4-bit long mark, 4-bit long space,14-bit long mark, 6-bit long space}. The address mark AM shown in FIG.8B has a pattern composed of {4-bit long mark, 14-bit long space, 6-bitlong mark, 6-bit long space, 14-bit long mark, 4-bit long space}. Theaddress mark AM shown in FIG. 8C has a pattern composed of {5-bit longmark, 14-bit long space, 5-bit long mark, 5-bit long space, 14-bit longmark, 5-bit long space}. The address mark AM shown in FIG. 8D has apattern composed of {4-bit long mark, 14-bit long space, 4-bit longmark, 4-bit long space, 14-bit long mark, 4-bit long space}.

[0103] In all of the above patterns, the total number of bits of themarks and the total number of bits of the spaces are equal to eachother. Thus, these patterns include two 14-bit long mark/spaces and alsoinclude a reduced amount of low-frequency components.

[0104] In the patterns shown in FIGS. 8A to 8D, the number of mark/spaceinversions is large compared with the patterns shown in FIGS. 7A to 7C.As the number of mark/space inversions increases, edge informationincreases and thus the error due to a bit shift occurs less easily. Inother words, the patterns shown in FIGS. 8A to 8D have a smallerprobability of causing erroneous synchronization detection due to a bitshift than the patterns shown in FIGS. 7A to 7C.

[0105] In some cases, the processing of a modulation circuit, ademodulation circuit, and the like becomes simpler if the address markAM has a length of an integer number of data bytes. FIG. 9 illustrates apattern of the address mark AM obtained by using a modulation code whichmodulates one data byte into 16 bits. The address mark AM is 48-bitlong, i.e., 3-data byte long. The pattern is composed of {4-bit longspace, 4-bit long mark, 14-bit long space, 4-bit long mark, 4-bit longspace, 14-bit long mark, 4-bit long space}.

[0106] The pattern of the address mark AM shown in FIG. 9 includes alarger number of mark/space inversions than the pattern shown in FIG.7A. As the number of mark/space inversions increases, edge informationincreases and thus the error due to a bit shift occurs less easily asdescribed above. In other words, the pattern shown in FIG. 9 has asmaller probability of causing erroneous synchronization detection dueto a bit shift than the pattern shown in FIG. 7A.

[0107]FIG. 10 is a block diagram of an optical disk device 100 forrecording/reproducing data on/from the optical disk 1 a having thesignal format described above. Referring to FIG. 10, the optical diskdevice 100 includes a spindle motor 7, a head 8, a preamplifier 9, amodulation circuit 11, a laser driving circuit 14, a reproduction system16, a system control 18, and a servo system 50.

[0108] The spindle motor 7 rotates the optical disk 1 a at apredetermined number of revolutions. The head 8 incorporates asemiconductor laser, an optical system, an optical detector, and thelike therein though these components are not shown. Laser light emittedby the semiconductor laser is converged by the optical system so that alight spot having a predetermined power for recording or reproduction isformed on a recording surface of the optical disk 1 a to realize datarecording/reproduction. Reflected light from the recording surface isconverged by the optical system and converted into a current by theoptical detector. The signal current output from the head 8 is furtherconverted into a voltage and amplified by the preamplifier 9, so as tobe output as a reproduced signal 10.

[0109] The servo system 50 performs the rotational control of thespindle motor 7, the phase control for moving the head 8 in the radialdirection of the optical disk 1 a, the focusing control for focusing thelight spot on the recording surface of the optical disk 1 a, and thetracking control for tracking the light spot along the center of thetrack.

[0110] The modulation circuit 11 performs the (2,10) modulation forinput data 12, and outputs modulated data 13 to the laser drivingcircuit 14. During the reproduction, the laser driving circuit 14outputs a laser driving signal 15 for driving the semiconductor laserincorporated in the head 8 to emit light with the power forreproduction. During the recording, the laser driving circuit 14 outputsthe laser driving signal 15 for driving the semiconductor laser to emitlight with the power for recording so that the mark length recording isperformed on the data recording region 4 in accordance with the suppliedmodulated data 13.

[0111] The reproduction system 16 reproduces various data recorded onthe header region 2 and the data recording region 4 from the reproducedsignal 10 supplied from the preamplifier 9, and outputs the data asreproduced data 17.

[0112] The system control 18 controls the operations of the modulationcircuit 11, the laser driving circuit 14, the reproduction system 16,and the servo system 50 based on the reproduced data 17 reproduced bythe reproduction system 16 and a user's configuration 19.

[0113]FIG. 11 is a block diagram illustrating an example of the internalconstruction of the reproduction system 16. Hereinbelow, the method forreproducing address information 40 recorded on the header region 2 fromthe reproduced signal 10 will be described. As shown in FIG. 11, thereproduction system 16 includes a clock reproduction circuit 20, abinary circuit 21, a VFO detection circuit 25, a reproduction permitcircuit 32, an address demodulation circuit 30, and a data demodulationcircuit 39.

[0114] The reproduced signal 10 received from the preamplifier 9 isinput into the clock reproduction circuit 20 and the binary circuit 21.The clock reproduction circuit 20 includes a PLL for generating areproduction clock 22 synchronized with the reproduced signal 10 infrequency and phase. The binary circuit 21 equalizes the waveform of thereproduced signal 10 as required, to convert the signal into a binarypattern composed of “1” and “0”. The binary circuit 21 outputs theconverted pattern itself to the VFO detection circuit 25 as asynchronousbinary data 23, and simultaneously synchronizes the converted binarypattern with the reproduction clock 22 supplied from the clockreproduction circuit 20 to output as synchronous binary data 24. Thesynchronous binary data 24 is supplied to the address demodulationcircuit 30 and the data demodulation circuit 39.

[0115] The VFO detection circuit 25 detects the sequential patternsrecorded on the VFO regions VF01, VF02, VF03, and VF04 based on theasynchronous binary data 23, and outputs a VFO detection pulse 26 ifpredetermined sequential patterns are detected.

[0116]FIG. 12A illustrates an example of the internal construction ofthe VFO detection circuit 25. As shown in FIG. 12A, the VFO detectioncircuit 25 includes a parallel conversion circuit 28, an oscillator 41,and a VFO detection table 42. The parallel conversion circuit 28receives the asynchronous binary data 23 and a fixed clock 27 generatedby the oscillator 41. The parallel conversion circuit 28 latches theasynchronous binary data 23 at the timing of the fixed clock 27 andconverts the asynchronous binary data 23 into parallel data 29corresponding to continuous 32 clocks. The converted parallel data 29 isinput into the VFO detection table 42.

[0117] The VFO detection table 42 is, for example, composed of a tableas shown in FIG. 12B which provides one-bit output from 32-bit input.The VFO detection table 42 outputs the VFO detection pulse 26 of “1” ifthe parallel data 29 sequentially input at the timing of the fixed clock27 is a pattern composed of four-time repetition of an 8-bit pattern,{11110000} or {00001111}, or a pattern similar to this pattern.Otherwise, the VFO detection pulse 26 is “0”.

[0118] The first two lines of patterns in the VFO detection table shownin FIG. 12B are detection patterns which are obtained when the frequencyof the fixed clock 27 is substantially equal to the frequency of thereproduction clock and completely match with the 4-bit long mark/spacerepetition pattern, i.e., the recording pattern of the VFO region. Theother patterns in the third and subsequent lines are more or lessdifferent from the recording pattern of the VFO region. These patternsare provided so that patterns can be detected even in the case where theamplitude of the reproduced signal 10 varies or in the case where thefrequency of the fixed clock 27 and the frequency of the reproductionclock become more or less different from each other due to a rotationalfluctuation of the optical disk 1 a.

[0119] By using the VFO detection circuit 25 with the above internalconstruction, the signals recorded on the VFO region can be detectedwith the fixed clock 27 corresponding to the frequency of a clockreproduced when the optical disk 1 a is rotating at a predeterminednumber of revolutions.

[0120] In this example, the parallel data 29 corresponding to 32 clocksare used for the detection of four periods of the 4-bit long mark/spacepattern. The number of bits of the parallel data 29 is not limited tothis number. An optimal number of bits may be selected so that anerroneous detection and an omission of detection are minimized. Thefrequency of the fixed clock 27 is not limited to the above-mentionedvalue. For example, if the frequency of the fixed clock is made tocorrespond to a quarter of the frequency of the reproduction clock, thepattern, {10101010} or {01010101} can be detected as the VFO pattern.

[0121] The VFO detection circuit 25 is not limited to the circuit havingthe internal construction shown in FIG. 12A. For example, since thesequential pattern includes a specific frequency component, such aspecific frequency component may be detected directly from thereproduced signal 10 to detect the sequential pattern.

[0122] The address demodulation circuit 30 detects the address mark AMusing the synchronous binary data 24 and the reproduction clock 22,performs the (2,10) demodulation for the modulated data recorded on thesubsequent address information regions ID1, ID2, ID3, and ID4, anddetects an error in the demodulated data.

[0123] In this example, as described above, each header region 2 iscomposed of four repeated address regions each including the VFO region,the address mark AM, and the address information region ID. Accordingly,when address information is successfully reproduced without an errorfrom two or more address information regions among the four addressinformation regions ID1, ID2, ID3, and ID4, the reproduced values areoutput to the system control 18 as the address information 40. Theaddress demodulation circuit 30 also outputs a sector synchronizationpulse 31 simultaneously with the output of the address information 40.

[0124] The four repeated recordings on the address regions will now bedescribed. The error rate for one address is about 10⁻². Assuming thatthe address information is obtained (the address is readable) when atleast two address regions among the four address regions aresuccessfully reproduced, the probability of failing to obtain theaddress information is as follows.

₄ C ₃×(10⁻²)³×(1−10⁻²)+(10⁻²)⁴≈4×10⁻⁶

[0125] wherein “₄C₃” is the number of combinations of three from four.Since one optical disk includes about 10⁶ recording sectors, the numberof recording sectors in which an address is not readable in one opticaldisk is 10⁶×(4×10⁻⁶)=4, which is within an allowable range. Thus, inthis example, the number of recording sectors in which addresses are notreadable is substantially reduced to less than 10. This facilitates theidentification of each recording with an extremely high probability. Asa result, each recording sector can be identified by reliably retrievingthe address information from the address regions of the header of eachrecording sector, without the necessity of providing a sector mark SMfor identifying the header at the start of the header.

[0126] For comparison, the conventional header 104 (FIG. 2B) includingthree address regions will be described. Assuming that the address isreadable (the address information is obtained) when at least two addressregions among the three address regions are successfully reproduced, theprobability of failing to obtain the address information is as follows.

₄ C ₃×(10⁻²)²×(1−10⁻²)+(10⁻²)³≈3×10⁻⁴

[0127] wherein “₃C₂” is the number of combinations of two from three.Since one optical disk includes about 10⁶ recording sectors, the numberof recording sectors in which an address is not readable in one opticaldisk is 10⁶×(3×10⁻⁴)=300, which is too large to be allowable.

[0128] Returning to FIG. 11, the reproduction permit circuit 32generates a clock reproduction permit signal 34 based on the VFOdetection pulse 26 supplied from the VFO detection circuit 25 and areproduction gate signal 33 supplied from the system control 18, andoutputs the signal to the clock reproduction circuit 20. The clockreproduction circuit 20 generates the reproduction clock 22 bysynchronizing the incorporated PLL with the phase of the reproducedsignal 10 and outputs the reproduction clock to the binary circuit 21only when the input clock reproduction permit signal 34 is “1”.

[0129] The reproduction permit circuit 32 also generates an addressreproduction permit signal 36 based on the VFO detection pulse 26 and anaddress gate signal 35 from the system control 18, and outputs thesignal to the address demodulation circuit 30. The address demodulationcircuit 30 detects the address mark AM by identifying the pattern of theaddress mark AM in the above-described manner only when the inputaddress reproduction permit signal 36 is “1”.

[0130] The reproduction permit circuit 32 further generates a datareproduction permit signal 38 based on the VFO detection pulse 26 and adata gate signal 37 from the system control 18, and outputs the signalto the data demodulation circuit 39. The data demodulation circuit 39demodulates recorded data read from the data recording region 4 amongthe synchronous binary data 24 and outputs the reproduced data 17 onlywhen the input data reproduction permit signal 38 is “1”.

[0131] The system control 18 outputs the reproduction gate signal 33,the address gate signal 35, and the data gate signal 37 at a timing inaccordance with the information format shown in FIGS. 5B and 5C (i.e.,the reproduced signal format) using the sector synchronization pulse 31supplied from the address demodulation circuit 30 of the reproductionsystem 16 as the reference. These signals are supplied to thereproduction permit circuit 32 of the reproduction system 16 asdescribed above (FIG. 11).

[0132]FIG. 13 illustrates exemplary waveforms of the sectorsynchronization pulse 31, the reproduction gate signal 33, the addressgate signal 35, and the data gate signal 37 to show the relationshipbetween these signals.

[0133] Referring to FIG. 13, the reproduced signal format conforms tothe information recording format shown in FIG. 5B. The header region 2,the gap region 3, and the data recording region 4 of a recording sector1A are called a header region 2 a, a gap region 3 a, and a datarecording region 4 a. Likewise, the header region 2, the gap region 3,and the data recording region 4 of a recording sector 1B following therecording sector 1A are called a header region 2 b, a gap region 3 b,and a data recording region 4 b.

[0134] In the recording sector 1A, when the address information iscorrectly reproduced from the header region 2 a, the sectorsynchronization pulse 31 becomes “1” (high level) somewhere in the rangefrom the end of the header region 2 a through the gap region 3 a. Thereproduction gate signal 33 becomes “1” over the range at least coveringthe data recording region 4 a of the recording section 1A and the headerregion 2 b of the next recording sector 1B. The address gate signal 35becomes “1” over the range at least covering the header region 2 b ofthe next recording sector 1B. The data gate signal 37 becomes “1” overthe range substantially covering the data recording region 4 a of therecording sector 1A.

[0135] The system control 18 may be constructed so as to first examinethe contents of the address information 40 together with the sectorsynchronization pulse 31 and determine whether or not the recordingsectors 1A and 1B have address information to be recorded or reproducedbefore setting the respective gate signals to “1” in accordance with thetiming described above.

[0136]FIG. 14 illustrates exemplary waveforms of the VFO detection pulse26, the sector synchronization pulse 31, the reproduction gate signal33, the clock reproduction permit signal 34, the address gate signal 35,the address reproduction permit signal 36, the data gate signal 37, andthe data reproduction permit signal 38, shown in correspondence with thesignal format.

[0137] Referring to FIG. 14, it is assumed that an information addressis first correctly reproduced from the recording sector 1A and that thedata recording regions 4 a and 4 b of the recording sectors 1A and 1Bhave no data recorded thereon but a data recording region 4 c of a nextrecording sector 1C has data thereon. Also assumed is that the beginningof the data recording region 4 c includes a sequential patternsubstantially equal to that on the VFO region, which is composed of4-bit long marks and spaces appearing alternately.

[0138] The clock reproduction permit signal 34 is “1” for apredetermined time period after the VFO detection pulse 26 of “1”appears. The clock reproduction permit signal 34 is also “1” over thetime period when the reproduction gate signal 33 is “1”. The abovepredetermined time period is at least equal to the time period requiredto read the address marks AM and the address information regions ID1,ID2, ID3, and ID4 of the header region 2. As a result, when the VFOdetection pulse 26 becomes “1” for the respective VFO regions of therecording sector 1A, the clock reproduction permit signal 34 remains “1”until at least the end of the header region 2 a. When the addressinformation has been correctly reproduced in the recording sector 1A andthe sector synchronization pulse 31 is output, the clock reproductionpermit signal 34 becomes “1” for the header region 2 b of the nextrecording sector 1B without fail. Likewise, when the address informationhas been correctly reproduced in the recording sector 1B and the sectorsynchronization pulse 31 is output, the clock reproduction permit signal34 becomes “1” for the header region 2 c of the next recording sector 1Cwithout fail.

[0139] The address reproduction permit signal 36 is “1” for apredetermined time period after the VFO detection pulse 26 becomes “1”and for a time period when the address gate signal 35 is “1”. The abovepredetermined time period is set to at least equal to the total timeperiod required to read information from the address marks AM and theaddress information regions ID1, ID2, ID3, and ID4. As a result, whenthe VFO detection pulse becomes “1” for the respective VFO regions ofthe recording sector 1A, the address reproduction permit signal 36remains “1” until at least the end of the header region 2 a. When theaddress information has been correctly reproduced in the recordingsector 1A and the sector synchronization pulse 31 is output, the addressreproduction permit signal 36 becomes “1” for the header region 2 b ofthe next recording sector 1B without fail. Likewise, when the addressinformation has been correctly reproduced in the recording sector 1B andthe sector synchronization pulse 31 is output, the address reproductionpermit signal 36 becomes “1” for the header region 2 c of the nextrecording sector IC without fail.

[0140] The data reproduction permit signal 38 becomes “1” if the datagate signal 37 is “1” when the VFO detection pulse 26 rises to “1”, andremains “1” until the data gate signal 37 becomes “0”. The datareproduction permit signal 38 remains “0” if the data gate signal 37 is“0” when the VFO detection pulse 26 rises to “1”. As a result, since theVFO detection pulse 26 does not become “1” for the date recordingregions 4 a and 4 b where no data has been recorded, the datareproduction permit signal 38 remains “0”. For the data recording region4 c where data has been recorded, the VFO detection pulse becomes “1” atthe header portion thereof. Accordingly, the date reproduction permitsignal 38 becomes “1” at a predetermined timing.

[0141] Thus, by using the VFO detection circuit 25 and the reproductionpermit circuit 32, the clock reproduction and the reproduction of theaddress information are permitted in the header region 2 so that theclock signal and the address information can be read. As describedabove, the sector synchronization pulse 31 is output after the addressinformation is reproduced from the header region 2 (see FIG. 13).According to the present invention, therefore, the address informationof the recording sector can be read even in the state where the timereference by the sector synchronization pulse 31 is not available.

[0142] Also, by using the system control 18, the address demodulationcircuit 30, and the reproduction permit circuit 32, once addressinformation has been reproduced from one recording sector (e.g., therecording sector 1A) without an error, the clock reproduction and thereproduction of the address information in the header region 2 ispermitted for the recording sector 1A and the next recording sector 1B,and the clock reproduction and the reproduction of the data in thecorresponding data recording regions 4 are permitted. Accordingly, onceaddress information has been reproduced from one recording sector, theaddress information and the data can be read in a more secured mannerusing the sector synchronization pulse 31 as the reference.

[0143] In the above example, the system control 18 generates three typesof gate signals using the sector synchronization pulse 31, while thereproduction permit circuit 32 generates three types of permit signalsusing the VFO detection pulse 26 and the three types of gate signals.Alternatively, the system control 18 may have the function of thereproduction permit circuit 32 so that the system control 18 candirectly generate the three types of permit signals.

[0144]FIG. 15 is a flowchart showing an example of a process performedwhen, after the switching-on of the optical disk device 100 (FIG. 10),the system control 18 outputs the clock reproduction permit signal 34and the address reproduction permit signal 36 using the VFO detectionpulse 26 and the sector synchronization pulse 31.

[0145] When the optical disk device 100 is switched on, the systemcontrol 18 first performs a boosting processing (step 1). The boostingprocessing includes the control of the rotation of the spindle motor 7by the servo system 50, the control of the movement of the head 8, thecontrol of the power of the semiconductor laser of the head 8, thefocusing control of the optical system, the tracking control, and thelike. In the boosting processing, both the clock reproduction permitsignal 34 and the address reproduction permit signal 36 are reset to“0”.

[0146] Once the head 8 is positioned above a predetermined track of theoptical disk 1 a by tracking, the VFO region is detected in the mannerdescribed above (step 2). When the “1” level of the VFO detection pulseis detected, the clock reproduction permit signal 34 is set at “1” (step3). Subsequently, the address reproduction permit signal 36 is set at“1” (step 4). After the lapse of a predetermined time period, theaddress reproduction permit signal 36 and the clock reproduction permitsignal 34 are reset to “0” again (step 5), and the sectorsynchronization pulse 31 is detected (step 6).

[0147] The sector synchronization pulse 31 becomes “1” when the addressdemodulation circuit 30 reads address information correctly. Insynchronization with this pulse signal, the address information 40output from the address demodulation circuit 30 is read, so as todetermine whether or not it indicates a target recording sector (step7). If the read address information 40 indicates the target recordingsector, the process proceeds to the control for recording/reproduction(step 8). If the read address information 40 does not indicate thetarget recording sector, the process proceeds to the seek control (step9).

[0148] If the address demodulation circuit 30 fails to read the addressinformation, the sector synchronization pulse 31 will not become “1” fora predetermined time period at step 6. In such a case, the processreturns to step 2 for the VFO detection.

[0149] With the process along the flow described above, the clockreproduction permit signal 34 and the address reproduction permit signal36 are generated at the timing as shown in FIG. 14. Thus, smooth readingof address information is possible even in the state observed beforeaddress information is reproduced immediately after the switching-on ofthe device, where the time reference by the sector synchronization pulse31 has not yet been provided.

[0150]FIG. 16 is a flowchart showing an example of a process performedby the system control 18 for switching the processing mode between theinitial mode and the normal mode. The initial mode as used hereincorresponds to the time period from the switching-on of the device or atrack jump to perform a seek and the like until the address informationis first reproduced. The normal mode corresponds to the time periodafter a predetermined address information has been read until a nexttrack jump is generated.

[0151] Referring to FIG. 16, the processings from step 1 through step 9are the same as corresponding processings in FIG. 15. The descriptionthereof is therefore omitted here.

[0152] As shown in FIG. 16, at step 10, whether the mode is the initialmode or the normal mode is determined. When the address information hasbeen correctly read and recording/reproduction at the target recordingsector has been performed in the preceding processings, the mode isdetermined to be the normal mode. The mode is determined to be theinitial mode after the boosting processing (step 1), after the readingof the address information is unsuccessful at step 6, or after theaddress information which has been successfully read is determined notto be the target recording sector at step 7 and the seek control isperformed (step 9).

[0153] In the normal mode, the VFO detection processing (step 2) is notperformed, but the processings of steps 3, 4, and 5 are performed usingthe timing at which the sector synchronization pulse 31 becomes “1” asthe reference. In the initial mode, the VFO detection processing (step2) is first performed, followed by the processings of steps 3, 4, and 5using the timing at which the VFO detection pulse 26 becomes “1” as thereference.

[0154] With the above processings, address information can be readsmoothly after the switching-on of the device or after a track jump,and, after the reproduction of the address information, the addressinformation and the data can be read in a more ensuring manner using thesector synchronization pulse 31 as the reference.

[0155] Thus, in the first example, the method for recording/reproducingdata on/from the optical disk 1 a having the signal format shown inFIGS. 5B and 5C by use of the optical disk device 100 having the blockconstruction shown in FIG. 10, especially, the method for readingaddress information, was described.

[0156] In the first example, the (2, 10) modulation code is used as themodulation code for the address information regions ID of the headerregion 2 and the data recording region 4. It will be appreciated,however, that the modulation code is not restricted to the above, andany type of run length limit code having a fixed maximum inversioninterval may be used. The pattern of the address mark AM may bedetermined so that the above conditions for the maximum inversioninterval T_(max) are satisfied.

[0157] In the first example, the information recorded on the VFO regionshas been described to be a pattern composed of sequential 4-bit longmarks/spaces shown in FIG. 6. It is appreciated, however, that thepattern for the VFO regions is not restricted to this pattern, and anypattern may be used in which the length of each mark or space is equalto or more than the minimum inversion interval T_(min) and less than themaximum inversion interval T_(max) of the modulation code (run lengthlimit code) used for the recording on the address information region ID.As described above, however, since a shorter mark/space pattern having alength closer to the minimum inversion interval T_(min) is morepreferable since the number of repetition periods per unit length islarger and thus a faster clock reproduction is obtained.

[0158] In this example, the patterns shown in FIGS. 7A to 7C, FIGS. 8Ato BD, and FIG. 9 were described as examples of the address marks AM.The patterns of the address marks AM are not restricted to thesepatterns. The detection of the address marks AM is possible if thepattern includes two repetitions of a pattern having a length of 3 ormore bits added to the maximum inversion interval T_(max) of themodulation code (run length limit code) used for the recording of theaddress information regions ID.

[0159] In this example, the header region 2 is composed of four addressregions. The header region 2 is not restricted to this construction. Forexample, the reproduction of address information is possible by theconstruction of the header region which includes only one addressregion. However, the reliability of the reading of the addressinformation can be improved by forming a plurality of address regions IDwhere substantially the same address information is stored. As describedabove, in consideration of the error rate for the address informationand the allowance of the number of unrecognizable recording sectors, itis preferable to form four or more address regions for one header region2. Furthermore, in view of the practical allowance and the maximumsecurement of the data recording regions 4, it is more preferable forthe header to include four address regions ID as described in the firstexample.

EXAMPLE 2

[0160]FIG. 17A is a view illustrating a format of a recording sector 51of an optical disk of the second example according to the presentinvention. As shown in FIG. 17A, the recording sector 51 starts with aheader region 52 where addressing information for reading addressinformation is prerecorded. A gap region 53, a data recording region 54,a postamble PA0, and a buffer region 55 respectively follow the headerregion 52 in this order.

[0161] The gap region 53 has no data recorded thereon, but is used forpower control of a semiconductor laser used for datarecording/reproduction and the like, for example. The data recordingregion 54 is used to record user data. Redundant data such as an errorcorrection code is added to the user data, to form digital data. Thedigital data is modulated using a run length limit code generated by useof a state machine. The modulated data is recorded on the data recordingregion 54 using the mark length recording. This run length limit code iscalled a state modulation code. The postamble PA0 follows the end of thedata recording region 54. The pattern of the postamble PA0 is determinedbased on the modulation results of the data recording region 54. Thebuffer region 55 is provided to absorb a rotational shift of the opticaldisk and the like. In the header region 52, information may be recordedas pits in a concave and convex shape on the recording surface, or asmarks optically recorded in substantially the same manner as that usedin the recording on the data recording region.

[0162] As shown in FIG. 17B, the header region 52 is divided into fouraddress regions 56 a, 56 b, 56 c, and 56 d. Each of the address regionsincludes a VFO region, an address mark AM, an address information regionID, and a postamble PA. For example, the address region 56 a includes aVFO region VF01, an address mark AM, an address information region ID1,and a postamble PA1, while the address region 56 b includes a VFO regionVF02, an address mark AM, an address information region ID2, and apostamble PA2. The address information regions ID1, ID2, ID3, and ID4will hereinafter be collectively referred to as the address informationregion ID. Also, the postambles PA1, PA2, PA3, and PA4 will hereinafterbe collectively referred to as the postamble PA.

[0163] In this example, as in the first example, no sector mark isrecorded on each header region 52, but the four address regions similarto one another, each composed of the VFO region, the address mark AM,the address information region ID, and the postamble PA, are recordedsequentially.

[0164] The VFO regions VF01, VF02, VF03, and VF04 are used so that anoptical disk device can obtain clock reproduction from a reproducedsignal. As in the first example, each VFO region has a sequentialpattern that includes marks and spaces of a fixed length (e.g., 4-bitlength) appearing alternately, for example. The VFO regions may have thesame length or different lengths. For example, if the head VFO regionVF01 is made longer than the other VFO regions, stable clockreproduction is obtained at the beginning of the header region 52.

[0165] Each address mark AM is provided so that the optical disk devicecan identify the position of the subsequent address information regionID. For example, like the address mark AM used in the first example, apattern including two repetitions of a pattern having a length of 3 bitsadded to the maximum inversion interval T_(max) of the state modulationcode is recorded.

[0166] On the address information region ID, digital data composed ofdata including address information such as the track number and thesector number with a predetermined error detection code added theretoare recorded using the mark length recording, after the digital data aremodulated using the state modulation code.

[0167]FIGS. 18A to 18C are conceptual views for explaining themodulation method and the demodulation method of the state modulationcode used in this example. The state modulation code is a modulationcode which converts an 8-bit binary data unit into a 16-bit codesequence. A 16-bit output code sequence Y_(t) for an 8-bit input dataD_(t) at a time t is determined based on a state S_(t) at the time t.FIG. 18A shows an exemplary construction of a state modulation circuit60. As shown in FIG. 18A, the state modulation circuit 60 includes aconversion table 56 and a D flipflop 57. The data D_(t) and the stateS_(t) at the time t are input into the conversion table 56, and the codesequence Y_(t) and a state S_(t+1) at a next time t+1 (hereinafter,referred to as a next state) are output therefrom. The next stateS_(t+1) output from the conversion table 56 is input into the D flipflop57 to be used for the next modulation.

[0168]FIG. 18B shows part of the content of the conversion table 56. Thestate S_(t) at the time t includes a total of four states from S_(t=)1to 4, and different code sequences Y_(t) are allocated to the respectivestates. The state S_(t) and the data D_(t) at the time t determine thenext state S_(t+1). The 16-bit sequences allocated as the output codesequences Y_(t) in the table are all the run length limit codes wherethe zero run is limited to the range of 2 to 10. Moreover, the nextstate S_(t+1) has been determined so that the zero run is still limitedto the range of 2 to 10 when the sequences at the two sequential timesare connected.

[0169] Among the 16-bit sequences allocated in the table as the outputcode sequences Y_(t), those of which next state S_(t+1) is 1 or 2 aredetermined so that the last zero run thereof is 5 or less.

[0170] There is a case where the same output sequence Y_(t) is allocatedto different input data units D_(t), like patterns p1 and p2 shown bythe underlines in the table. In such a case, the next states for theseoutput sequences are determined to be either state 2 or state 3 so as tobe different from each other. In this case, for example, the pattern p1has the next state 2, while the pattern p2 has the next state 3. Exceptfor such a case, no double allocation of the same output sequence Y_(t)will be found.

[0171] The code sequences Y_(t) allocated to state 2 and state 3 havethe following features. The output sequence Y_(t) allocated to state 2has “0”s at the first and thirteenth bits from left. The output sequenceY_(t) allocated to state 3 has “1”s at either the first bit or thethirteenth bit from left.

[0172] In the demodulation of the state modulation code, the 16-bit codesequence Y_(t) must be converted into an 8-bit binary data unit. FIG.18C is a block diagram for explaining the construction of a demodulationcircuit 61. In the demodulation circuit 61, the 16-bit code sequenceY_(t) at a time t and a first bit Y_(t+) _(—) ₁ and a thirteenth bitY_(t+1) _(—) ₁₃ of a code sequence Y_(t+1) at a next time t+1, i.e., atotal of 18 bits, are input into an inverse conversion table 58. Theoutput from the inverse conversion table 58 at the time t is an 8-bitbinary data unit D_(t).

[0173] The inverse conversion table 58 shown in FIG. 18B basicallycorresponds to an inverse view of the conversion table 56. For patternswhich have not been allocated double among the code sequences Y_(t), thebinary data unit D_(t) as the demodulation result thereof is uniquelydetermined.

[0174] For a pattern which has been allocated double, like the patternp1 and p2 in state 1 shown in FIG. 18B, the binary data unit D_(t)thereof cannot be uniquely determined. However, as described above, sucha double allocation of the same code sequence Y_(t) is limited to thecase where the next state thereof is state 2 or state 3. Accordingly, byrecognizing the difference between the code sequences of state 2 andstate 3, the original binary data unit D_(t) can be uniquely determined.In other words, the binary data unit D_(t) is uniquely determined byobserving the first and thirteenth bits of the code sequence at the timet+1 which is the code sequence determined by the next state at the timet during the modulation.

[0175] In the address information region ID, data including the addressinformation modulated in the modulation method as described above isrecorded using the mark length recording.

[0176] The postamble PA0 shown in FIG. 17A indicates the end of the datarecording region 54, and has a pattern determined based on the modulatedresults of the data recording region 54.

[0177] The postambles PA1, PA2, PA3, and PA4 shown in FIG. 17B indicatethe ends of the address regions 56 a to 56 d, respectively, and havepatterns determined based on the modulation results of the correspondingaddress information regions ID1, ID2, ID3, and ID4 recorded immediatelybefore the postambles.

[0178]FIGS. 19A and 19B show examples of patterns of the postambles. Thenext state shown in FIGS. 19A and 19B indicates the next state obtainedwhen the immediately preceding data unit has been modulated. In otherwords, for the postamble PA0, it indicates the next state obtained whenthe end data of the data recording region 54 has been modulated. For thepostambles PA1, PA2, PA3, and PA4, it indicates the next states obtainedwhen the end data of the address information regions ID1, ID2, ID3, andID4 have been modulated. In the case where the next state is state 1 orstate 2, a pattern p3 shown in FIG. 19A is selected as the postamble. Inthe case where the next state is state 3 or state 4, a pattern p4 shownin FIG. 19B is selected as the postamble. The selected postambles arerecorded using the mark length recording.

[0179] When the pattern p3 follows any of the code sequences where thenext state is state 1 or state 2, the zero run is still limited to therange of 2 to 10 at the coupling portion. When the pattern p4 followsany of the code sequences where the next state is state 3 or state 4,the zero run is still limited to the range of 2 to 10 at the couplingportion. Therefore, the run length limit will not be broken by addingthe postamble. The first and thirteenth bits of the pattern p3 are both“0”, while the first bit of the pattern p4 is “1”.

[0180] By using the patterns p3 and p4 as the postambles, patternsrecorded at the end of the data recording region 54 and the addressinformation regions ID1, ID2, ID3, and ID4 can be uniquely demodulated.

[0181] As another feature, the second, twelfth, and fourteenth bits ofthe pattern p3 which are bits adjacent to the specific bits foridentifying the state (the first and thirteenth bits) are all “0”. Thisprevents the state from being mistakenly modulated by recognizing thethirteenth bit as “1” due to a bit shift and the like.

EXAMPLE 3

[0182]FIG. 20A schematically illustrates an optical disk 201 a of thethird example according to the present invention. Referring to FIG. 20A,the optical disk 201 a has tracks 201 b formed on the surface thereof ina spiral shape. Each track 201 b is divided into recording sectors 201 cin accordance with a predetermined physical format. As shown in FIG.20A, the recording sectors 201 c are sequentially arranged in thecircumferential direction to form one track 201 b.

[0183]FIG. 20B illustrates a format of each recording sector 201 c ofthe optical disk 201 a of the third example according to the presentinvention. Referring to FIG. 20B, the recording sector 201 c starts witha header region 202 where addressing information for reading addressinformation is prerecorded. A gap region 203, a data recording region204, and a buffer region 205 follow the header region 202 in this order.The gap region 203 has no data recorded thereon, but is used for powercontrol of a semiconductor laser used for data recording/reproductionand the like. The data recording region 204 is used to record user data.Redundant data such as an error correction code is added to the userdata, to form digital data. The digital data is modulated using a runlength limit code where the zero run is limited to the range of 2 to 10,i.e., a (2,10) modulation code. The modulated data is recorded on thedata recording region 204 using the mark length recording. The bufferregion 205 is provided to absorb a rotational shift of the optical diskand the like. In the header region 202, information may be recorded aspits in a concave and convex shape on the recording surface, or as marksoptically recorded in substantially the same manner as that used in therecording on the data recording region.

[0184] As shown in FIG. 20C, the header region 202 is divided into fouraddress regions 206 a, 206 b, 206 c, and 206 d. Each of the addressregions includes a VFO region, an address mark AM, an addressinformation region ID, and a postamble PA. For example, the addressregion 206 a includes a VFO region VF01, an address mark AM, an addressinformation region ID1, and a postamble PA1, while the address region206 b includes a VFO region VF02, an address mark AM, an addressinformation region ID2, and a postamble PA2. The address informationregions ID1, ID2, ID3, and ID4 are hereinafter collectively referred toas the address information region ID. Also, the postambles PA1, PA2,PA3, and PA4 are hereinafter collectively referred to as the postamblePA.

[0185] In this example, as in the above examples, no sector mark isrecorded on each header region 202, but the four address regions, eachcomposed of the VFO region, the address mark AM, the address informationregion ID, and the postamble PA, are recorded sequentially.

[0186] The VFO regions VF01, VF02, VF03, and VF04 are used so that anoptical disk device can obtain clock reproduction from a reproducedsignal. As in the first example, for example, each VFO region has such asequential pattern that includes marks and spaces of a fixed length(e.g., 4-bit length) appearing alternately. The VFO regions may have thesame length or different lengths. For example, if the head VFO regionVF01 is made longer than the other VFO regions, stable clockreproduction is obtained at the beginning of the header region 202.

[0187] Each address mark AM is provided so that the optical disk devicecan identify the position of the subsequent address information region.For example, as in the address mark AM used in the first example, apattern including twice repetition of a pattern having a length of 3bits added to the maximum inversion interval T_(max) of the modulationcode (run length limit code) is recorded.

[0188] On the address information region ID, digital data composed ofdata including address information such as the track number and thesector number with a predetermined error detection code added theretoare recorded using the mark length recording, after the digital data ismodulated using the state modulation code.

[0189]FIG. 21A shows an arrangement of the address regions of the headerregion 202 recorded on the recording surface of the optical disk of thisexample. As shown in FIG. 21A, in the optical disk, information isrecorded on both groove tracks and land tracks. The reference numerals210 and 212 denote the groove tracks, while the reference numeral 211denotes the land track. Address regions 213 to 220 are formed so as tooverride the adjacent groove tracks and land tracks. The address regions213 and 217 correspond to the address region 206 a. The address regions214 and 218 correspond to the address region 206 b. The address regions215 and 219 correspond to the address region 206 c. The address regions216 and 220 correspond to the address region 206 d. The distance betweenthe center line of the land track and the center line of the groovetrack is a track pitch Tp. Each address region is displaced from thecenterline of the track by T_(p)/2 toward inside or outside of the disk.For example, the address regions 213 to 216 are alternately arranged onboth sides of the groove track 210 with respect to the centerlinethereof. The reference numeral 207 denotes a light spot. During thereproduction, address information is read from the address regions 213to 216 along the groove track 210, and from the address regions 217,214, 219, and 216 along the land track 211. By arranging the addressregions in the above manner, it is possible to read the addressinformation from both the land tracks and the groove tracks.

[0190] Hereinbelow, a method for forming a prototype for producing astamper used for the fabrication of a disk substrate havingconvex-shaped groove tracks and the address regions as concave andconvex shaped pits described above will be described. The tracks and theaddress regions are formed by irradiating the rotating disk prototypewith laser light for cutting. By continuous radiation of laser light,the groove track having one continuous groove is formed. By intermittentON/OFF radiation of laser light, portions irradiated with laser lightare formed as marks (pit data) in the address regions. The otherportions which have not been irradiated with the laser light are left asspaces (non-pit data). For example, a predetermined pattern as describedin the above examples is recorded by a combination of the marks and thespaces. In this example, the address regions are arranged to bedisplaced inside and outside the center of the track (wobblingarrangement). Accordingly, the ON/OFF radiation of laser light isperformed by shifting the center of the laser light for cutting in theradial direction by a predetermined amount T_(p)/2 for every addressregion. Incidentally, at the production of the disk prototype, thecutting is performed from the surface opposite the surface which is tobe the recording surface at the reproduction operation. Therefore, theconcave and convex portions of the pits and the grooves at theproduction of the disk prototype are reverse to those as are viewed fromthe reproduction head at the reading operation.

[0191]FIG. 21B shows another arrangement of the address regions of theheader region 202 recorded on the recording surface of the optical diskof this example. In the optical disk shown in FIG. 21B, information isrecorded on both groove tracks and land tracks. The reference numerals210 and 212 denote the groove tracks, while the reference numeral 211denotes the land track. Address regions 213 to 220 are formed so as tooverride the adjacent groove tracks and land tracks. The address regions213 and 217 correspond to the address region 206 a. The address regions214 and 218 correspond to the address region 206 b. The address regions215 and 219 correspond to the address region 206 c. The address regions216 and 220 correspond to the address region 206 d. The distance betweenthe centerline of the land track and the centerline of the groove trackis a track pitch Tp. The two preceding address regions (213, 214, 217,218) are displaced outside the centerlines 230 of the groove tracks byT_(p)/2. The two subsequent address regions (215, 216, 219, 220) aredisplaced inside the centerlines 230 of the groove tracks by T_(p)/2.The reference numeral 207 denotes a light spot. During the reproduction,address information is read from the address regions 213 to 216 alongthe groove track 210, and from the address regions 217, 218, 215, and216 along the land track 211.

[0192] By arranging the address regions in the above manner, it ispossible to read the address information from both the land tracks andthe groove tracks.

[0193] Moreover, since every two address regions as a unit arealternately displaced inside and outside of the disk, the number oftimes at which the center of the laser light for cutting is shifted inthe radial direction by T/2 during the production of the disk prototypereduces, compared with the arrangement shown in FIG. 21A, facilitatingthe cutting of the prototype of the optical disk.

[0194] During the production of the prototype of the optical disk, asshown in FIG. 21A (FIG. 21B), the groove 210 and the address regions213, 214, 215, and 216 along the groove are first formed. Thereafter,after one rotation of the disk prototype, the groove 212 and the addressregions 217, 218, 219, and 220 along the groove are formed. At thistime, due to a variation in the rotational precision of the diskprototype and the like, the position of the address region 213 and theposition of the address region 217 which corresponds thereto along theradial direction of the optical disk do not necessarily match with eachother in the circumferential direction. If the ends of the addressregions 213 and 217 are displaced by ΔX as shown in FIG. 21A (FIG. 21B),the end of the address region 217 (218) and the beginning of the addressregion 214 (215) overlap with each other by ΔX when data on the landtrack 211 is reproduced. This may results in failure to reproduceaddress information correctly.

[0195] To overcome this problem, as shown in FIG. 21C, it is arranged sothat no mark is recorded but a space is provided at the end of eachaddress region and furthermore a space (ΔX1) longer than the rotationalprecision (ΔX) at the cutting of the disk prototype is provided at thebeginning of the next address region.

[0196] For example, the rotational precision at the cutting of the diskprototype is about 20 ns/revolution when the number of revolutions ofthe disk prototype is 700 rpm. Accordingly, in the case of an opticaldisk having a diameter of 120 mm, the value of ΔX is about 0.1 μm atmaximum when converted into a length.

[0197] The operation in the above case will be described.

[0198]FIGS. 22A and 22B schematically illustrate the coupling portion ofthe two address regions 213 (214) and 214 (215). In the data sequencesof the address regions shown in FIGS. 22A and 22B, the end (the finalpattern) of the address region 213 (214) includes a mark, and the headpattern of the subsequent address region 214 (215) also includes a mark.FIG. 22A shows an ideal mark shape expected for such a data arrangement.In other words, the mark at the end of the address region 213 (214) andthe mark at the beginning of the address region 214 (215) have apredetermined length and are formed at a center position of therespective address regions. In reality, however, when address pits areformed while shifting laser light for each address region in the cuttingprocess of the disk prototype, if the marks consecutively appear in thecoupling portion of the address region 213 (214) and the next addressregion 214 (215), the laser continues to emit laser light for cuttingwhile shifting in the radial direction. Accordingly, in reality, themark at the end of the address region 213 (214) and the mark at thebeginning of the address region 214 (215) are consecutively formed asshown in FIG. 22B, forming an incorrect mark overriding the two addressregions. As a result, correct data reproduction becomes difficult.

[0199]FIGS. 23A and 23B illustrate the reading operation when a lightspot 207 reproduces data from the land track 211.

[0200]FIG. 23A illustrates the case where the mark arrangement in thecoupling portion of two adjacent address regions is not specificallyconsidered. As shown in FIG. 23A, when the adjacent address regions 214(215) and 217 (218) spatially overlap by a cutting precision ΔX, dataread from the two address regions temporally overlap by an amountcorresponding to ΔX. While the end of the address region 217 (218)includes a space, the beginning of the address region 214 (215) includesa mark. As shown in FIG. 23A, when the space at the end of the addressregion 217 (218) is overlapped by the mark at the beginning of theaddress region 214 (215), the end of the address region 217 (218) isregarded as having the mark. This causes a data error at the addressregion 217 (218).

[0201]FIG. 23B illustrates a data arrangement according to the presentinvention for overcoming the above problem. As shown in FIG. 23B, spacesare arranged at the end and the beginning of the adjacent addressregions. With this arrangement, even if the space at the end of theaddress region 217 (218) is overlapped by the space at the beginning ofthe address region 214 (215), the overlapping portion is still a space,generating no data error on the address region 217 (218). This mayresult in failing to read correctly the length of the space at thebeginning of the address region 214 (215). However, the beginning ofeach address region includes the VFO region and, generally, it is notnecessarily required to read all data on the VFO region. Moreover, noproblem arises in the reading operation of the address region as far asthe synchronization of the address region is recovered by the addressmark AM following the VFO region so that the address information can becorrectly recognized.

[0202] Also, at the cutting of the disk prototype, a space is alwaysarranged between adjacent address regions to prevent marks from beingcontinuously formed. Accordingly, the continuous radiation of laserlight while shifting in the radial direction is prevented. Accordingly,the formation of a defect mark as shown in FIG. 22B is prevented.

[0203] Thus, by arranging spaces at the head and the end of each addressregion as shown in FIG. 23B, the failure in mark formation at thecutting of the disk prototype and the erroneous data reading due to theoverlap of the address regions at the data reproduction from the addressregions in the case of the wobbling arrangement of the address regionscan be prevented.

[0204] Hereinbelow, the case of applying the mark arrangement of thepostamble PA in this example to the data arrangement using the statemodulating code described in Example 2 (FIGS. 18A and 18B) will bedescribed. FIGS. 24A to 24D illustrate exemplary mark arrangements ofthe postamble PA in the case of using the state modulation code. InFIGS. 24A to 24D, the next state indicates the next state obtained whenthe immediately preceding data has been modulated, in other words, thenext state obtained when the data at the end of the correspondingaddress information region ID has been modulated.

[0205]FIG. 24A shows the case where the next state is either state 1 orstate 2 (see FIG. 18B) and the end of the address information region IDis a mark 240. In this case, a pattern p5 as shown in FIG. 24A,{0010010010000000}, is selected and recorded using the mark lengthrecording. As described in Example 2, since the last zero run in thecode sequence of which next state is either state 1 or state 2 is 5 orless, when any of the code sequences of which next state is either state1 or state 2 is coupled with the pattern p5, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p5 are both “0”. Also, by selecting thepattern p5, the end of the postamble PA, i.e., the end of the addressregion is always a space.

[0206] Accordingly, since both the head and the end of each addressregion are spaces, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions may beprevented.

[0207] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the coupling portion of theadjacent address regions always includes a 11-bit long space which isthe maximum inversion interval. This makes it possible to increase thetime for the movement of a laser beam at the cutting while the limit ofthe zero run of the run length limit code is maintained.

[0208] As a further feature of the pattern p5, the second, twelfth, andfourteenth bits which are bits adjacent to the specific bits foridentifying the state (the first and thirteenth “0” bits) are all “0”.This prevents the state from being mistakenly modulated by recognizingthe thirteenth bit as “1” due to a bit shift and the like.

[0209] The pattern of the postamble PA is not limited to the pattern p5shown in this example. Any pattern can be used as far as the number ofzeros in the zero run satisfies the limit of the run length limit codeused for the address information region ID, the state information is 1or 2, the pattern is different from that of the address mark AM, and thepattern includes an odd number of “1”s.

[0210]FIG. 24B illustrates the case where the next state is either state1 or state 2 (see FIG. 18B) and the end of the address informationregion ID is a space. In this case, a pattern p6 as shown in FIG. 24B,{0000010010000000}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 1 or state 2 is coupled with the pattern p6, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p6 are both “0”. Also, by selecting thepattern p6, the end of the postamble PA, i.e., the end of the addressregion is a space. Accordingly, both the head and the end of eachaddress region are spaces. Therefore, the failure in mark formation atthe cutting of the disk prototype and the erroneous data reading due tothe overlap of address regions at the data reproduction of the addressregions in the case of the wobbling arrangement of the address regionsmay be prevented.

[0211] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the coupling portion of theadjacent address regions always includes a 11-bit long space which isthe maximum inversion interval. This makes it possible to increase thetime for the movement of a laser beam at the cutting while the limit ofthe zero run of the run length limit code is maintained.

[0212] As a further feature of the pattern p6, the second, twelfth, andfourteenth bits which are bits adjacent to the specific bits foridentifying the state (the first and thirteenth “0” bits) are all “0”.This prevents the state from being mistakenly modulated by mistakenlyrecognizing the thirteenth bit as “1” due to a bit shift and the like.

[0213] The pattern of the postamble PA is not limited to the pattern p6shown in this example. Any pattern can be used as far as the number ofzeros in the zero run satisfies the limit of the run length limit codeused for the address information region ID, the state information is 1or 2, the pattern is different from that of the address mark AM, and thepattern includes an even number of “1”s.

[0214]FIG. 24C shows the case where the next state is either state 3 orstate 4 (see FIG. 18B) and the end of the address information region IDis the mark 240. In this case, a pattern p7 as shown in FIG. 24C,{1000010010000000}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p7, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p7 is “1”. Also, by selecting the pattern p7, the end ofthe postamble PA, i.e., the end of the address region is always a space.Accordingly, both the head and the end of each address region arespaces.

[0215] Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions may beprevented.

[0216] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the coupling portion of theadjacent address regions always includes a 11-bit long space which isthe maximum inversion interval. This makes it possible to increase thetime for the movement of a laser beam at the cutting while the limit ofthe zero run of the run length limit code is maintained.

[0217] The pattern of the postamble PA is not limited to the pattern p7shown in this example. Any pattern can be used as far as the number ofzeros in the zero run satisfies the limit of the run length limit codeused for the address information region ID, the state information is 3or 4, the pattern is different from that of the address mark AM, and thepattern includes an odd number of “1”s.

[0218]FIG. 24D shows the case where the next state is either state 3 orstate 4 (see FIG. 18B) and the end of the address information region IDis a space. In this case, a pattern p8 as shown in FIG. 24D,{1000000010000000}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p8, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p8 is “1”. Also, by selecting the pattern p8, the end ofthe postamble PA, i.e., the end of the address region is always a space.Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions may beprevented.

[0219] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the coupling portion of theadjacent address regions always includes a 11-bit long space which isthe maximum inversion interval. This makes it possible to increase thetime for the movement of a laser beam at the cutting while the limit ofthe zero run of the run length limit code is maintained.

[0220] The pattern of the postamble PA is not limited to the pattern p8shown in this example. Any pattern can be used as far as the number ofzeros in the zero run satisfies the limit of the run length limit codeused for the address information region ID, the state information is 3or 4, the pattern is different from that of the address mark AM, and thepattern includes an even number of “1”s.

[0221]FIGS. 24E to 24H illustrate alternative examples of markarrangement of the postamble PA in the case of using the statemodulation code. In FIGS. 24E to 24H, the next state indicates the nextstate obtained when the immediately preceding data has been modulated,in other words, the next state obtained when the data at the end of thecorresponding address information region ID has been modulated.

[0222]FIG. 24E illustrates the case where the next state is either state1 or state 2 (see FIG. 18B) and the end of the address informationregion ID is the mark 240. In this case, a pattern p9 as shown in FIG.24E, {0000010000010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 1 or state 2 is coupled with the pattern p9, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p9 are “0”. Also, by selecting thepattern p9, the end of the postamble PA, i.e., the end of the addressregion is a space.

[0223] Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions may beprevented.

[0224] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . .}, the 4-bit long mark at the end ofthe postamble can be used as the VFO.

[0225]FIG. 24F illustrates the case where the next state is either state1 or state 2 (see FIG. 18B) and the end of the address informationregion ID is a space. In this case, a pattern p10 as shown in FIG. 24F,{0001000100010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 1 or state 2 is coupled with the pattern p10, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first andthirteenth bits of the pattern p10 are “0”. Also, by selecting thepattern p10, the end of the postamble PA, i.e., the end of the addressregion is a space.

[0226] Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the data reproduction of the address regions in thecase of the wobbling arrangement of the address regions can beprevented.

[0227] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the 4-bit long mark at the endof the postamble can be used as the VFO.

[0228]FIG. 24G illustrates the case where the next state is either state3 or state 4 (see FIG. 18B) and the end of the address informationregion ID is the mark 240. In this case, a pattern p11 as shown in FIG.24G, {1000100100010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p11, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p11 is “1”. Also, by selecting the pattern p11, the endof the postamble PA, i.e., the end of the address region is a space.

[0229] Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the reproduction of the address regions in the caseof the wobbling arrangement of the address regions may be prevented.

[0230] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the 4-bit long mark at the endof the postamble can be used as the VFO.

[0231]FIG. 24H illustrates the case where the next state is either state3 or state 4 (see FIG. 18B) and the end of the address informationregion ID is a space. In this case, a pattern p12 as shown in FIG. 24H,{1000010000010001}, is selected and recorded using the mark lengthrecording. When any of the code sequences of which next state is eitherstate 3 or state 4 is coupled with the pattern p12, the zero run at thecoupling portion is still limited to the range of 2 to 10. The first bitof the pattern p12 is “1”. Also, by selecting the pattern p12, the endof the postamble PA, i.e., the end of the address region is a space.

[0232] Accordingly, both the head and the end of each address region arespaces. Therefore, the failure in mark formation at the cutting of thedisk prototype and the erroneous data reading due to the overlap ofaddress regions at the reproduction of the address regions in the caseof the wobbling arrangement of the address regions can be prevented.

[0233] Moreover, by setting the pattern of the VFO region arranged atthe beginning of each address region at a sequential pattern signalstarting with {000100010001000 . . . }, the 4-bit long mark at the endof the postamble can be used as the VFO.

[0234] Exemplary arrangements of the above-described patterns of thepostamble PA will be described. As an example, postambles having thepatterns p5 to p8 shown in FIGS. 24A to 24D may be used as thepostambles PA1, PA2, PA3, and PA4 shown in FIG. 20C. Alternatively,postambles having the patterns p9 to p12 shown in FIGS. 24E to 24H maybe used as the postambles PA1, PA2, PA3, and PA4 shown in FIG. 20C.

[0235] Alternatively, the postambles having the patterns p5 to p8 shownin FIGS. 24A to 24D may be used as the postambles PA2 and PA4 shown inFIG. 20C, while the postambles having the patterns p9 to p12 shown inFIGS. 24E to 24H may be used as the postambles PA1 and PA3 shown in FIG.20C. In this case, when the address regions on the disk are arranged asshown in FIG. 21B, the ends of the address regions 213 and 215 can beused as the VFO regions between the address regions 213 and 214 andbetween the address regions 215 and 216, respectively, where theshifting of the laser light for cutting is not required. Also, a 11-bitlong space can be secured between the address regions 214 and 215 wherethe shifting of the laser light for cutting is required. In this way,both the merits of the two types of patterns can be obtained. Moreover,in this case, by setting the length of VF01 and VF03 larger than thelength of VF02 and VF04, stable clock reproduction is obtained at theheading address regions 213 and 215 in the wobbling arrangement.

EXAMPLE 4

[0236]FIG. 25A illustrates a format of a recording sector 61 of anoptical disk of the fourth example according to the present invention.The recording sector 61 starts with a header region 62 where addressinginformation for reading address information is prerecorded. A gap region63, a data recording region 64, a postamble 65, a guard data recordingregion 66, and a buffer region 67 follow the header region 62 in thisorder. The gap region 63 has no data recorded thereon, but is used forpower control of a semiconductor laser used for datarecording/reproduction and the like, for example. The data recordingregion 64 is used to store user data. Redundant data such as an errorcorrection code is added to the user data, to form digital data. Thedigital data is modulated using a predetermined run length limit code,and recorded on the data recording region 64 using the mark lengthrecording.

[0237] The postamble 65 indicates the end of the data recording region64. The pattern of the postamble 65 is determined based on themodulation results of the data recording region 64. The postamble 65includes information used at the modulation of data, like the stateidentification bit described in the second example. The guard datarecording region 66 is provided to suppress a degradation of therecording surface due to repeated recording of data on the samerecording sector, and includes dummy data which does not have specificinformation. The buffer region 67 is provided to absorb a rotationalshift of the optical disk and the like.

[0238] Data is recorded on the data recording region 64, the postamble65, and the guard data region 66 by irradiating the regions with a lightspot having a predetermined recording power to form optical marks on therecording surface. In general, the crystal structure of a thin film ofthe recording surface is changed into an amorphous state, to change thereflection characteristic of the mark portions. Thus, since a light spothaving a comparatively large power is formed for the data recording, therecording surface bears a heat load. This causes a degradation of therecording surface.

[0239] In particular, in each recording sector, the difference in theheat load is generated at the boundary between a region where data hasbeen recorded and a region where data has not been recorded. When datarecording is repeated, the material of the recording film shifts due tothe difference in the heat load. This may degrade the boundary region,thereby making it difficult to read data correctly. When such an opticaldisk that may be degraded at the recording surface due to repeatedrecording is used, important data should preferably be prevented frombeing recorded in the vicinity of the boundary where the difference inthe heat load may be generated. In this example, in order to overcomethe above problem, the guard data recording region 66 is provided. Theguard data recording region 66 includes dummy data, which providessubstantially the same level of heat load as that generated at therecording of data on the data recording region 64 or the postamble 65.In the data patterns written on the data recording region 64 and thepostamble 65, low-frequency components increase when the number of themarks or spaces appearing in the patterns exceeds majority. The increasein the low-frequency components is not preferable because it varies thenumber of reproduced signal components in a servo band, affecting theservo system. Thus, the number of the low-frequency components in thepatterns is desirably as small as possible. In many cases, therefore,the modulation is performed so that the total number of bits for marksand the total number of bits for spaces are as close as possible to eachother.

[0240] Accordingly, in the pattern of the dummy data recorded on theguard data recording region 66, also, the total number of bits for marksis preferably equal to the total number of bits for spaces. With thisarrangement, the heat load of the dummy data is in substantially thesame level as the heat load generated at the recording of data on thedata recording region 64 and the postamble 65.

[0241] For example, a pattern where a k-bit long mark and a k-bit longspace are alternately repeated for an even number of times may be used,wherein k is a natural number satisfying T_(min)≦k≦T_(max); T_(min) andT_(max) are the minimum and maximum inversion intervals, respectively,of the run length limit code.

[0242] The guard data recording region 66 preferably has a length of aninteger number of data bytes because such a length facilitates theprocessings of the modulation circuit, the demodulation circuit, and thelike.

[0243]FIG. 25B illustrates an example of a pattern recorded on the guarddata recording region 66 when such a modulation code that modulates onedata byte into 16 bits (T_(min)=3, T_(max)=11) as was described abovewith reference to FIG. 18B is used. This pattern is composed ofalternate repetition of 4-bit long mark and space, and has a totallength of 16×n bits (n is a natural number).

[0244] In FIG. 25B, the dummy data starts with a mark. It would beunderstood that the pattern may also start with a space depending on thepattern at the end of the postamble 65.

[0245] Since the total number of bits for the marks is equal to thetotal number of bits for the spaces, the heat load of the pattern shownin FIG. 25B is in substantially the same level as the heat loadgenerated at the recording of data on the data recording region 64 andthe postamble 65. Therefore, the degradation of the recording film dueto the difference in the heat load may be prevented.

[0246] Since the above pattern satisfies the conditions for the minimuminversion interval and the maximum inversion interval of the modulationcode (run length limit code), it will not affect the reproduction ofdata from the header region and the data region.

INDUSTRIAL APPLICABILITY

[0247] As described above, in an optical disk according to the presentinvention, address synchronous information and address informationmodulated using the run length limit code are recorded on the headerregion of each recording sector. The pattern of the address synchronoussignal includes two patterns having a length larger than the maximuminversion interval T_(max) of the run length limit code by 3 bits ormore. With this pattern, the reproduced signal of the addresssynchronous information is distinguished from the reproduced signal ofother information, thereby preventing easy occurrence of erroneousdetection of the address synchronous information. This makes it possibleto perform stable bit synchronization for reproduction of addressinformation using the address synchronization information without thenecessity of forming a sector mark in each recording sector.

[0248] The address synchronous information is recorded using first andsecond patterns which are different in either a physical shape or anoptical characteristic of the recording surface of the optical disk. Forexample, the first pattern is a convex portion (pit) formed physicallyon the recording surface thereof, and the second pattern is a concaveportion formed physically on the recording surface of the optical disk.Alternatively, the first pattern is a recording mark formed by changingthe reflection characteristic of the recording surface of the opticaldisk, and the second pattern is a space on the recording surface. Theaddress synchronous information includes one first pattern having alength of (T_(max)+3) bits or more and one second pattern having alength of (T_(max)+3) bits or more, so that the address synchronousinformation can be distinguished from other data modulated by the runlength limit code even when an error arises due to a bit shift and thelike.

[0249] By equalizing the total bit length of the first pattern includedin the header region and the total bit length of the second patternincluded therein, the amount of low-frequency components contained inthe pattern may be reduced. This will prevent the stability of the servosystem from being lost during the data reproduction from the headerregion.

[0250] The header region includes four-time repetition of the addressinformation and the address synchronous information. This reduces thenumber of defective recording sectors where address information is notreadable in the optical disk with high recording density in an allowablerange. Thus, the present invention provides a high-quality optical disk.

[0251] In an optical disk according to the present invention, the headerregion of each recording sector includes address information foridentifying the position of the corresponding recording sector, addresssynchronous information for identifying the recording position of theaddress information for bit synchronization, and clock synchronousinformation for reproducing the clock signal. The address informationhas been modulated using a run length limit code of a minimum inversioninterval of T_(min) bits and a maximum inversion interval of T_(max)bits (T_(max) and T_(min) are natural numbers satisfyingT_(max)>T_(min)). The clock synchronous information is a sequentialpattern of alternate repetition of d-bit long mark and space (where d isa natural number satisfying T_(min)≦d≦T_(max)) The address synchronousinformation includes two patterns of which inversion interval is(T_(max)+3) bits or more, so that the reproduced signal of the addresssynchronous information is distinguished from the reproduced signal ofother information. Faster clock reproduction is possible by reading thesequential pattern of alternate repetition of the d-bit long mark andspace. Also, stable bit synchronization for reproducing the addressinformation is possible by reading the address synchronous information.

[0252] In an optical disk according to the present invention, a pattern(sector mark) composed of a long mark for identifying the start of arecording sector is not recorded at the beginning of the recordingsector. This reduces the overhead amount of data as a format. At thesame time, as described above, both the detection of the beginning ofthe recording sector and the clock reproduction can be performed usingthe clock synchronous information.

[0253] In an optical disk according to the present invention, eachrecording sector includes the header region and the postamble regionfollowing the end of the header region, and the postamble regionincludes a pattern determined based on the modulation result of data ofthe header region. Accordingly, in the case where the data of the headerregion has been modulated using a modulation code for performing aconversion in a table based on a state, for example, the postamble caninclude therein information for state identification. This allows forefficient demodulation of data in the header region.

[0254] In an optical disk according to the present invention, eachrecording sector includes the header region, the data recording region,and the postamble region following the end of the data recording region,wherein the postamble region includes a pattern determined based on themodulation result of data on the data recording region. Accordingly, inthe case where the data of the data recording region has been modulatedusing a modulation code for performing a conversion in a table based ona state, for example, the postamble can include therein information forstate identification. This also allows for efficient demodulation ofdata in the data recording region.

[0255] The recording sector further includes the guard data recordingregion following the postamble region for recording dummy data. Theguard data recording region includes a pattern of alternate repetitionof a k-bit long optical mark and a k-bit long optical space, wherein kis a natural number satisfying T_(min)≦k≦T_(max). This arrangement ofthe guard data region prevents the recording surface from being degradeddue to repeated recording, as well as preventing the reliability ofrecorded data from being lost.

[0256] In an optical disk according to the present invention, eachrecording sector includes the header region, and the header regionincludes the address region having the postamble region at the end ofthe address region, and the postamble region has a pattern which endswith non-pit data or a space. The header region includes a plurality ofaddress regions, and the VFO region at the beginning of each addressregion has a pattern which starts with non-pit data or a space.Alternatively, non-pit data or a space having a length of T_(max) bitsis provided between the address regions. With the above arrangement, inthe case of recording the address regions in the middle of the landtracks and the groove tracks, the formation of marks in the optical diskfabrication process is facilitated, and moreover erroneous reading ofinformation from the address regions may be prevented.

[0257] An optical disk device according to the present inventionincludes: means for reading a reproduced signal from the optical disk;address reproduction means for obtaining the address information fromthe reproduced signal; detection means for detecting the sequentialpattern of the clock synchronous information from the reproduced signalto output a detection signal; and address reproduction permit means forpermitting the address reproduction means to perform a read operation ofthe address information based on the detection signal. With thisconstruction, stable and efficient reproduction of address informationis possible for an optical disk which does not include a sector mark (apattern composed of a long mark for identifying the start of a recordingsector) at the beginning of each recording sector, by detecting thesequential pattern of the clock synchronous information. Theconventional optical disk includes both a sector mark and clocksynchronous information on the header region. According to the presentinvention, since no sector mark is required, the date recording regioncan be increased.

[0258] An optical disk device according to the present inventionincludes: clock generation means for generating a clock signal from thereproduced signal; and clock reproduction permit signal for permittingthe clock generation means to perform an operation of generating theclock signal based on the detection signal of the sequential pattern ofthe clock synchronous information. With this construction, stable andefficient reproduction of the clock signal is possible for an opticaldisk which does not include a sector mark at the beginning of eachrecording sector, by detecting the sequential pattern of the clocksynchronous information.

[0259] A reproduction method for an optical disk according to thepresent invention includes the steps of: retrieving a reproduced signalfrom the optical disk; detecting the sequential pattern of the clocksynchronous information from the reproduced signal; permitting readingof the address information if the sequential pattern is detected;reading the address information from the reproduced signal in responseto the permission; and terminating the step of reading the addressinformation in a predetermined time period after the permission toreturn to the step of detecting the sequential pattern. With thismethod, stable reading of the address information at the switching-on ofthe device or immediately after a track jump is possible for an opticaldisk having no sector mark but having clock synchronous information of apredetermined sequential pattern.

[0260] A reproduction method for an optical disk according to thepresent invention includes the steps of: retrieving a reproduced signalfrom the optical disk; detecting the sequential pattern of the clocksynchronous information from the reproduced signal; permittingreproduction of a clock signal if the sequential pattern is detected;and reproducing the clock signal from the reproduced signal in responseto the permission. With this method, stable reproduction of the clocksignal at the switching-on of the device or immediately after a trackjump is possible for an optical disk having no sector mark foridentifying the start of the recording sector, but having clocksynchronous information of a predetermined sequential pattern.

[0261] A reproduction method for an optical disk includes the steps of:retrieving a reproduced signal from the optical disk; determining areproduction mode whether the reproduction mode is an initial modeduring a time period from the switching-on of the device or a track jumpuntil the address information is first read from the reproduced signalor a normal mode during a time period from the reading of the addressinformation until a next track jump is generated; detecting thesequential pattern of the clock synchronous information from thereproduced signal; permitting reading of the address information if thesequential pattern is detected in the initial mode as a first permittingstep; reading the address information from the reproduced signal inresponse to the permission; generating a sector pulse if the addressinformation is correctly read; permitting reading of the addressinformation from the reproduced signal based on the sector pulse in thenormal mode as a second permitting step; and terminating the reading ofthe address information to return to the step of determining areproduction mode if the address information fails to be read within apredetermined time period after either the first or second permissionstep. With this method, the processing after the switching-on of thedevice or a track jump until the address information is first reproducedand the processing at the normal data reproduction can be switchedtherebetween. Thus, efficient and reliable reading of the addressinformation of each recording sector is possible.

[0262] By combining the optical disk according to the present inventionwith the optical disk device according to the present invention, or bycombining the optical disk of the present invention with the opticaldisk reproduction method, further stable and efficient reading of theaddress information is possible even in the case where the recordingdensity of the optical disk is improved by the technique such as themark length recording and the land/groove recording.

1. An optical disk comprising a plurality of tracks each divided into aplurality of recording sectors, each of the recording sectors includinga header region, wherein the header region includes address informationfor identifying a position of the corresponding recording sector andaddress synchronous information for identifying a recording position ofthe address information for bit synchronization, the address informationhas been modulated using a run length limit code of a maximum inversioninterval of T_(max) bits (T_(max) is a natural number), and the addresssynchronous information includes two patterns of which inversioninterval is (T_(max)+3) bits or more, so that a reproduced signal of theaddress synchronous information is distinguished from a reproducedsignal of other information.
 2. An optical disk according to claim 1,wherein the address synchronous information includes a first pattern anda second pattern which are different in either a physical shape or anoptical characteristic of a recording surface of the optical disk, andthe address synchronous information includes one first pattern having alength of (T_(max)+3) bits or more and one second pattern having alength of (T_(max)+3) bits or more.
 3. An optical disk according toclaim 2, wherein the first pattern is a convex portion (pit) formedphysically on the recording surface of the optical disk, and the secondpattern is a concave portion formed physically on the recording surfaceof the optical disk.
 4. An optical disk according to claim 2, whereinthe first pattern is a recording mark formed by changing a reflectioncharacteristic of the recording surface of the optical disk, and thesecond pattern is a space on the recording surface.
 5. An optical diskaccording to claim 2, wherein a total bit length of the first patternincluded in the address synchronous information and a total bit lengthof the second pattern included in the address synchronous informationare equal to each other.
 6. An optical disk according to claim 1,wherein the header region includes four-time repetition of the addressinformation and the address synchronous information.
 7. An optical diskcomprising a plurality of tracks each divided into a plurality ofrecording sectors, each of the recording sectors including a headerregion, wherein the header region includes address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation for reproducing a clock signal, the address information hasbeen modulated using a run length limit code of a minimum inversioninterval of T_(min) bits and a maximum inversion interval of T_(max)bits (T_(max) and T_(min) are natural numbers satisfyingT_(max)>T_(min)), the clock synchronous information is a sequentialpattern of alternate repetition of d-bit long mark and space (d is anatural number satisfying T_(min)≦d≦T_(max)), and the addresssynchronous information includes two patterns of which inversioninterval is (T_(max)+3) bits or more, so that a reproduced signal of theaddress synchronous information is distinguished from a reproducedsignal of other information.
 8. An optical disk according to claim 7,wherein each of the address synchronous information and the clocksynchronous information includes a first pattern and a second patternwhich are different in either a physical shape or an opticalcharacteristic of a recording surface of the optical disk, and theaddress synchronous information includes one first pattern having alength of (T_(max)+3) bits or more and one second pattern having alength of (T_(max)+3) bits or more.
 9. An optical disk according toclaim 7, wherein the minimum inversion interval T_(min) is 3, themaximum inversion interval T_(max) is 11, and the value d is
 3. 10. Anoptical disk according to claim 7, wherein the minimum inversioninterval T_(min) is 3, the maximum inversion interval T_(max) is 11, andthe value d is
 4. 11. An optical disk according to claim 7, wherein theheader region includes four-time repetition of the clock synchronousinformation, the address information, and the address synchronousinformation.
 12. An optical disk comprising a plurality of tracks eachdivided into a plurality of recording sectors, wherein each recordingsector includes a header region and a postamble region following an endof the header region, and the postamble region includes a patterndetermined based on a modulation result of data of the header region.13. An optical disk according to claim 12, wherein the data on theheader region is modulated using a modulation code for performing aconversion in a table based on a state, the postamble region includesinformation for identifying the state.
 14. An optical disk according toclaim 13, wherein the information for identifying the state is at leastone specific bit having a predetermined value, and a bit locatedadjacent to the specific bit has substantially the same value as thepredetermined value of the specific bit.
 15. An optical disk comprisinga plurality of tracks each divided into a plurality of recordingsectors, wherein each recording sector includes a header region, a datarecording region, and a postamble region following an end of the datarecording region, and the postamble region includes a pattern determinedbased on a modulation result of data of the data recording region. 16.An optical disk according to claim 15, wherein the data on the datarecording region is modulated using a modulation code for performingconversion in a table based on a state, the postamble region includesinformation for identifying the state.
 17. An optical disk according toclaim 16, wherein the information for identifying the state is at leastone specific bit having a predetermined value, and a bit locatedadjacent to the specific bit has substantially the same value as thepredetermined value of the specific bit.
 18. An optical disk accordingto claim 15, wherein the recording sector further includes a guard datarecording region following the postamble region for recording dummydata.
 19. An optical disk according to claim 18, wherein the datarecording region includes data modulated using a run length limit codeof a minimum inversion interval of T_(min) bits and a maximum inversioninterval of T_(max) bits (T_(max) and T_(min) are natural numberssatisfying T_(max)>T_(min)), and the guard data recording regionincludes a pattern of repetition of a k-bit long optical mark and ak-bit long optical space (k is a natural number satisfyingT_(min)≦k≦T_(max)).
 20. An optical disk comprising a plurality of trackseach divided into a plurality of recording sectors, wherein eachrecording sector includes a header region, and the header regionincludes an address region having a postamble region at an end of theaddress region, and the postamble region has a pattern which ends withnon-pit data or a space.
 21. An optical disk according to claim 20,wherein the header region includes a plurality of the address regions.22. An optical disk according to claim 20, wherein the address regionsare located in the middle of groove portions and land portions of thetracks.
 23. An optical disk comprising a plurality of tracks eachdivided into a plurality of recording sectors, wherein each recordingsector includes a header region, the header region includes a pluralityof address regions, each of the address regions includes a VFO region ata beginning of the address region, and the VFO region has a patternwhich starts with non-pit data or a space.
 24. An optical disk accordingto claim 23, wherein the address region includes an address informationregion where address information is recorded using a mark lengthrecording for identifying a position of the corresponding recordingsector, and the address information is modulated using a run lengthlimit code of a minimum inversion interval of T_(min) bits and a maximuminversion interval of T_(max) bits (T_(max) and T_(min) are naturalnumbers satisfying T_(max)>T_(min)), and non-pit data or a space havinga length in a range of T_(min) bits or more and T_(max) bits or less isprovided between the address regions.
 25. An optical disk according toclaim 24, wherein the address regions are located in the middle ofgroove portions and land portions of the tracks.
 26. An optical diskdevice for an optical disk including a plurality of tracks each dividedinto a plurality of recording sectors, each recording sector including aheader region and a data region, the header region including addressinformation for identifying a position of the corresponding recordingsector, address synchronous information for identifying a recordingposition of the address information for bit synchronization, and clocksynchronous information having a predetermined sequential pattern, thedevice comprising: means for reading a reproduced signal from theoptical disk; address reproduction means for obtaining the addressinformation from the reproduced signal; detection means for detectingthe sequential pattern of the clock synchronous information from thereproduced signal to output a detection signal; and address reproductionpermit means for permitting the address reproduction means to perform aread operation of the address information based on the detection signal.27. An optical disk device according to claim 26, further comprising:clock generation means for generating a clock signal from the reproducedsignal; and clock reproduction permit signal for permitting the clockgeneration means to perform an operation of generating the clock signalbased on the detection signal.
 28. An optical disk device according toclaim 26, wherein the detection means comprises: binary means forconverting the reproduced signal into binary data to output the binarydata; sampling means for sampling the binary data at a predeterminedfrequency to output digital data; parallel conversion means forconverting the digital data into parallel data of at least m x n bits (mand n are natural numbers); and a detection table for detecting apredetermined sequence composed of n-time repetition of an m-bit patternfrom the parallel data.
 29. An optical disk device for an optical diskincluding a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the devicecomprising: means for reading a reproduced signal from the optical disk;clock generation means for generating a clock signal from the reproducedsignal; detection means for detecting the sequential pattern of theclock synchronous information from the reproduced signal to output adetection signal; and clock reproduction permit means for permitting theclock generation means to perform an operation of generating the clocksignal based on the detection signal.
 30. An optical disk deviceaccording to claim 29, wherein the detection means comprises: binarymeans for converting the reproduced signal into binary data to outputthe binary data; sampling means for sampling the binary data at apredetermined frequency to output digital data; parallel conversionmeans for converting the digital data into parallel data of at least m xn bits (m and n are natural numbers); and a detection table fordetecting a predetermined sequence composed of n-time repetition of anm-bit pattern from the parallel data.
 31. A reproduction method for anoptical disk including a plurality of tracks each divided into aplurality of recording sectors, each recording sector including a headerregion and a data region, the header region including addressinformation for identifying a position of the corresponding recordingsector, address synchronous information for identifying a recordingposition of the address information for bit synchronization, and clocksynchronous information having a predetermined sequential pattern, themethod comprising the steps of: retrieving a reproduced signal from theoptical disk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reading of theaddress information if the sequential pattern is detected; reading theaddress information from the reproduced signal in response to thepermission; and terminating the step of reading the address informationin a predetermined time period after the permission to return to thestep of detecting the sequential pattern.
 32. A reproduction method foran optical disk according to claim 31, further comprising the steps of:permitting reproduction of a clock signal if the sequential pattern isdetected; and reproducing the clock signal from the reproduced signal inresponse to the permission.
 33. A reproduction method for an opticaldisk including a plurality of tracks each divided into a plurality ofrecording sectors, each recording sector including a header region and adata region, the header region including address information foridentifying a position of the corresponding recording sector, addresssynchronous information for identifying a recording position of theaddress information for bit synchronization, and clock synchronousinformation having a predetermined sequential pattern, the methodcomprising the steps of: retrieving a reproduced signal from the opticaldisk; detecting the sequential pattern of the clock synchronousinformation from the reproduced signal; permitting reproduction of aclock signal if the sequential pattern is detected; and reproducing theclock signal from the reproduced signal in response to the permission.34. A reproduction method for an optical disk including a plurality oftracks each divided into a plurality of recording sectors, eachrecording sector including a header region and a data region, the headerregion including address information for identifying a position of thecorresponding recording sector, address synchronous information foridentifying a recording position of the address information for bitsynchronization, and clock synchronous information having apredetermined sequential pattern, the method comprising the steps of:retrieving a reproduced signal from the optical disk; determining areproduction mode whether the reproduction mode is an initial modeduring a time period from switching-on of the device or a track jumpuntil the address information is first read from the reproduced signalor a normal mode during a time period from the reading of the addressinformation until a next track jump is generated; detecting thesequential pattern of the clock synchronous information from thereproduced signal; permitting reading of the address information if thesequential pattern is detected in the initial mode as a first permittingstep; reading the address information from the reproduced signal inresponse to the permission; generating a sector pulse if the addressinformation is correctly read; permitting reading of the addressinformation from the reproduced signal based on the sector pulse in thenormal mode as a second permitting step; and terminating the reading ofthe address information to return to the step of determining areproduction mode if the address information fails to be read within apredetermined time period after either the first or second permissionstep.